In the Linux kernel, the following vulnerability has been resolved:

FS:JFS:UBSAN:array-index-out-of-bounds in dbAdjTree

Syzkaller reported the following issue:

UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dmap.c:2867:6 index 196694 is out of range for type s8[1365] (aka signed char[1365]) CPU: 1 PID: 109 Comm: jfsCommit Not tainted 6.6.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106 ubsan_epilogue lib/ubsan.c:217 [inline] __ubsan_handle_out_of_bounds+0x11c/0x150 lib/ubsan.c:348 dbAdjTree+0x474/0x4f0 fs/jfs/jfs_dmap.c:2867 dbJoin+0x210/0x2d0 fs/jfs/jfs_dmap.c:2834 dbFreeBits+0x4eb/0xda0 fs/jfs/jfs_dmap.c:2331 dbFreeDmap fs/jfs/jfs_dmap.c:2080 [inline] dbFree+0x343/0x650 fs/jfs/jfs_dmap.c:402 txFreeMap+0x798/0xd50 fs/jfs/jfs_txnmgr.c:2534 txUpdateMap+0x342/0x9e0 txLazyCommit fs/jfs/jfs_txnmgr.c:2664 [inline] jfs_lazycommit+0x47a/0xb70 fs/jfs/jfs_txnmgr.c:2732 kthread+0x2d3/0x370 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

Kernel panic - not syncing: UBSAN: panic_on_warn set … CPU: 1 PID: 109 Comm: jfsCommit Not tainted 6.6.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106 panic+0x30f/0x770 kernel/panic.c:340 check_panic_on_warn+0x82/0xa0 kernel/panic.c:236 ubsan_epilogue lib/ubsan.c:223 [inline] __ubsan_handle_out_of_bounds+0x13c/0x150 lib/ubsan.c:348 dbAdjTree+0x474/0x4f0 fs/jfs/jfs_dmap.c:2867 dbJoin+0x210/0x2d0 fs/jfs/jfs_dmap.c:2834 dbFreeBits+0x4eb/0xda0 fs/jfs/jfs_dmap.c:2331 dbFreeDmap fs/jfs/jfs_dmap.c:2080 [inline] dbFree+0x343/0x650 fs/jfs/jfs_dmap.c:402 txFreeMap+0x798/0xd50 fs/jfs/jfs_txnmgr.c:2534 txUpdateMap+0x342/0x9e0 txLazyCommit fs/jfs/jfs_txnmgr.c:2664 [inline] jfs_lazycommit+0x47a/0xb70 fs/jfs/jfs_txnmgr.c:2732 kthread+0x2d3/0x370 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304 Kernel Offset: disabled Rebooting in 86400 seconds..

The issue is caused when the value of lp becomes greater than CTLTREESIZE which is the max size of stree. Adding a simple check solves this issue.

Dave: As the function returns a void, good error handling would require a more intrusive code reorganization, so I modified Osamas patch at use WARN_ON_ONCE for lack of a cleaner option.

The patch is tested via syzbot.

Affected Software

References

• https://git.kernel.org/stable/c/42f433785f108893de0dd5260bafb85d7d51db03
• https://git.kernel.org/stable/c/59342822276f753e49d27ef5eebffbba990572b9
• https://git.kernel.org/stable/c/6a44065dd604972ec1fbcccbdc4a70d266a89cdd
• https://git.kernel.org/stable/c/6fe8b702125aeee6ce83f20092a2341446704e7b
• https://git.kernel.org/stable/c/9862ec7ac1cbc6eb5ee4a045b5d5b8edbb2f7e68
• https://git.kernel.org/stable/c/98f9537fe61b8382b3cc5dd97347531698517c56
• https://git.kernel.org/stable/c/de34de6e57bbbc868e4fcf9e98c76b3587cabb0b
• https://git.kernel.org/stable/c/e3e95c6850661c77e6dab079d9b5374a618ebb15