Comment 3 for bug 1902525

We are randomly getting the same segfault on two different servers, one with 18.04 and one with 20.04. Here is the strace output, if it helps:

xxx@yyy:~$ sudo strace btrfs subvolume list /mnt/btrfs
execve("/bin/btrfs", ["btrfs", "subvolume", "list", "/mnt/btrfs"], 0x7ffcd5a42ff8 /* 23 vars */) = 0
brk(NULL) = 0x5576268f3000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=26618, ...}) = 0
mmap(NULL, 26618, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f1d50e75000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libuuid.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0@\26\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=27112, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1d50e73000
mmap(NULL, 2122112, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1d50a4e000
mprotect(0x7f1d50a54000, 2093056, PROT_NONE) = 0
mmap(0x7f1d50c53000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x5000) = 0x7f1d50c53000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libblkid.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0000\230\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=311720, ...}) = 0
mmap(NULL, 2411776, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1d50801000
mprotect(0x7f1d50848000, 2097152, PROT_NONE) = 0
mmap(0x7f1d50a48000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x47000) = 0x7f1d50a48000
mmap(0x7f1d50a4d000, 3328, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f1d50a4d000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libz.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\220\37\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=116960, ...}) = 0
mmap(NULL, 2212016, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1d505e4000
mprotect(0x7f1d50600000, 2093056, PROT_NONE) = 0
mmap(0x7f1d507ff000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1b000) = 0x7f1d507ff000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/liblzo2.so.2", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0000#\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=137256, ...}) = 0
mmap(NULL, 2232416, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1d503c2000
mprotect(0x7f1d503e3000, 2093056, PROT_NONE) = 0
mmap(0x7f1d505e2000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x20000) = 0x7f1d505e2000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/x86_64-linux-gnu/libzstd.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\3604\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=501680, ...}) = 0
mmap(NULL, 2596912, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1d50147000
mprotect(0x7f1d501c1000, 2093056, PROT_NONE) = 0
mmap(0x7f1d503c0000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x79000) = 0x7f1d503c0000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libpthread.so.0", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0000b\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=144976, ...}) = 0
mmap(NULL, 2221184, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1d4ff28000
mprotect(0x7f1d4ff42000, 2093056, PROT_NONE) = 0
mmap(0x7f1d50141000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19000) = 0x7f1d50141000
mmap(0x7f1d50143000, 13440, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f1d50143000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260\34\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2030544, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1d50e71000
mmap(NULL, 4131552, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1d4fb37000
mprotect(0x7f1d4fd1e000, 2097152, PROT_NONE) = 0
mmap(0x7f1d4ff1e000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f1d4ff1e000
mmap(0x7f1d4ff24000, 15072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f1d4ff24000
close(3) = 0
mmap(NULL, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1d50e6e000
arch_prctl(ARCH_SET_FS, 0x7f1d50e6e8c0) = 0
mprotect(0x7f1d4ff1e000, 16384, PROT_READ) = 0
mprotect(0x7f1d50141000, 4096, PROT_READ) = 0
mprotect(0x7f1d503c0000, 4096, PROT_READ) = 0
mprotect(0x7f1d505e2000, 4096, PROT_READ) = 0
mprotect(0x7f1d507ff000, 4096, PROT_READ) = 0
mprotect(0x7f1d50c53000, 4096, PROT_READ) = 0
mprotect(0x7f1d50a48000, 16384, PROT_READ) = 0
mprotect(0x557625ce2000, 20480, PROT_READ) = 0
mprotect(0x7f1d50e7c000, 4096, PROT_READ) = 0
munmap(0x7f1d50e75000, 26618) = 0
set_tid_address(0x7f1d50e6eb90) = 6908
set_robust_list(0x7f1d50e6eba0, 24) = 0
rt_sigaction(SIGRTMIN, {sa_handler=0x7f1d4ff2dcb0, sa_mask=[], sa_flags=SA_RESTORER|SA_SIGINFO, sa_restorer=0x7f1d4ff3a8a0}, NULL, 8) = 0
rt_sigaction(SIGRT_1, {sa_handler=0x7f1d4ff2dd50, sa_mask=[], sa_flags=SA_RESTORER|SA_RESTART|SA_SIGINFO, sa_restorer=0x7f1d4ff3a8a0}, NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
brk(NULL) = 0x5576268f3000
brk(0x557626914000) = 0x557626914000
statfs("/mnt/btrfs", {f_type=BTRFS_SUPER_MAGIC, f_bsize=4096, f_blocks=1048576000, f_bfree=813464493, f_bavail=813322881, f_files=0, f_ffree=0, f_fsid={val=[2961959219, 47240398]}, f_namelen=255, f_frsize=4096, f_flags=ST_VALID|ST_NOATIME}) = 0
stat("/mnt/btrfs", {st_mode=S_IFDIR|0755, st_size=52, ...}) = 0
stat("/mnt/btrfs", {st_mode=S_IFDIR|0755, st_size=52, ...}) = 0
openat(AT_FDCWD, "/mnt/btrfs", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3
fstat(3, {st_mode=S_IFDIR|0755, st_size=52, ...}) = 0
ioctl(3, BTRFS_IOC_INO_LOOKUP, {treeid=0, objectid=256 /* BTRFS_FIRST_FREE_OBJECTID */} => {treeid=5 /* BTRFS_FS_TREE_OBJECTID */, name=""}) = 0
ioctl(3, BTRFS_IOC_INO_LOOKUP, {treeid=0, objectid=256 /* BTRFS_FIRST_FREE_OBJECTID */} => {treeid=5 /* BTRFS_FS_TREE_OBJECTID */, name=""}) = 0
ioctl(3, BTRFS_IOC_TREE_SEARCH, {key={tree_id=1 /* BTRFS_ROOT_TREE_OBJECTID */, min_objectid=5 /* BTRFS_FS_TREE_OBJECTID */, max_offset=18446744073709551615 /* UINT64_MAX */, max_transid=18446744073709551615 /* UINT64_MAX */, min_type=132 /* BTRFS_ROOT_ITEM_KEY */, max_type=144 /* BTRFS_ROOT_BACKREF_KEY */, nr_items=4096}} => {key={nr_items=28}, buf=...}) = 0
ioctl(3, BTRFS_IOC_TREE_SEARCH, {key={tree_id=1 /* BTRFS_ROOT_TREE_OBJECTID */, min_objectid=257, min_offset=1364, max_offset=18446744073709551615 /* UINT64_MAX */, max_transid=18446744073709551615 /* UINT64_MAX */, min_type=156 /* BTRFS_ROOT_REF_KEY */, max_type=144 /* BTRFS_ROOT_BACKREF_KEY */, nr_items=4096}} => {key={nr_items=42}, buf=...}) = 0
ioctl(3, BTRFS_IOC_TREE_SEARCH, {key={tree_id=1 /* BTRFS_ROOT_TREE_OBJECTID */, min_objectid=257, min_offset=12704, max_offset=18446744073709551615 /* UINT64_MAX */, max_transid=18446744073709551615 /* UINT64_MAX */, min_type=156 /* BTRFS_ROOT_REF_KEY */, max_type=144 /* BTRFS_ROOT_BACKREF_KEY */, nr_items=4096}} => {key={nr_items=40}, buf=...}) = 0
ioctl(3, BTRFS_IOC_TREE_SEARCH, {key={tree_id=1 /* BTRFS_ROOT_TREE_OBJECTID */, min_objectid=257, min_offset=13004, max_offset=18446744073709551615 /* UINT64_MAX */, max_transid=18446744073709551615 /* UINT64_MAX */, min_type=156 /* BTRFS_ROOT_REF_KEY */, max_type=144 /* BTRFS_ROOT_BACKREF_KEY */, nr_items=4096}} => {key={nr_items=30}, buf=...}) = 0
ioctl(3, BTRFS_IOC_TREE_SEARCH, {key={tree_id=1 /* BTRFS_ROOT_TREE_OBJECTID */, min_objectid=353, min_offset=1, max_offset=18446744073709551615 /* UINT64_MAX */, max_transid=18446744073709551615 /* UINT64_MAX */, min_type=1 /* BTRFS_INODE_ITEM_KEY */, max_type=144 /* BTRFS_ROOT_BACKREF_KEY */, nr_items=4096}} => {key={nr_items=29}, buf=...}) = 0
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x7ffcc950b22b} ---
+++ killed by SIGSEGV (core dumped) +++
Segmentation fault