apparmor backtraces for goldfish kernel

[John Johansen]

The goldfish kernel when apparmor is enable fills the logs with backtraces similar (there are several slightly different traces) to the following:

WARNING: at /build/buildd/linux-goldfish-3.4.0/security/apparmor/label.c:226 __aa_label_remove+0x54/0xd8()
AppArmor WARN __aa_label_remove: (((((void)(&(&ls->lock)->raw_lock), 1)))):
Modules linked in:
[<c0012864>] (unwind_backtrace+0x0/0x11c) from [<c001e774>] (warn_slowpath_common+0x4c/0x64)
[<c001e774>] (warn_slowpath_common+0x4c/0x64) from [<c001e80c>] (warn_slowpath_fmt+0x2c/0x3c)
[<c001e80c>] (warn_slowpath_fmt+0x2c/0x3c) from [<c01f6b84>] (__aa_label_remove+0x54/0xd8)
[<c01f6b84>] (__aa_label_remove+0x54/0xd8) from [<c01f75d4>] (aa_label_remove+0x28/0x5c)
[<c01f75d4>] (aa_label_remove+0x28/0x5c) from [<c01f7640>] (aa_label_kref+0x38/0x4c)
[<c01f7640>] (aa_label_kref+0x38/0x4c) from [<c01f888c>] (aa_label_parse+0x1d0/0x20c)
[<c01f888c>] (aa_label_parse+0x1d0/0x20c) from [<c01ecc48>] (query_label.constprop.4+0x210/0x334)
[<c01ecc48>] (query_label.constprop.4+0x210/0x334) from [<c01ecdf8>] (aa_write_access+0x8c/0xbc)
[<c01ecdf8>] (aa_write_access+0x8c/0xbc) from [<c00d2414>] (vfs_write+0xb0/0x128)
[<c00d2414>] (vfs_write+0xb0/0x128) from [<c00d2654>] (sys_write+0x3c/0x68)
[<c00d2654>] (sys_write+0x3c/0x68) from [<c000dc40>] (ret_fast_syscall+0x0/0x30)

[John Johansen (jjohansen)]

This bug occurs because apparmor is using the kernel macro
  can_write_lock()

in its AA_DEBUG asserts, however can_write_lock() does not work on non-smp kernels as the lock variable that is being tested is never updated, as the lock operations are removed.

[John Johansen (jjohansen)]

The following patch is needed

index 788ec21..39eae14 100644
--- a/security/apparmor/label.c
+++ b/security/apparmor/label.c
@@ -19,6 +19,10 @@
 #include "include/policy.h"
 #include "include/sid.h"

+#if !defined(CONFIG_SMP)
+#undef write_can_lock
+#define write_can_lock(X) 0
+#endif

 /*
  * the aa_label represents the set of profiles confining an object

[John Johansen (jjohansen)]

The goldfish kernel for saucy is not used nor supported so marking won't fix for saucy.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-goldfish - 3.4.0-1.10

---------------
linux-goldfish (3.4.0-1.10) trusty; urgency=low

  [ Andy Whitcroft ]

  * [Config] switch build-depends to libiberty-dev

  [ Dimitri John Ledkov ]

  * [Config] enable CONFIG_INPUT_UINPUT
    - LP: #1260023

  [ John Johansen ]

  * SAUCE: (no-up) apparmor: fix backtrace on non-smp, kernels.
    - LP: #1253707
 -- Andy Whitcroft <email address hidden> Wed, 11 Dec 2013 18:04:04 +0000