[PATCH 5.4 154/154] jfs: add index corruption check to DT_GETPAGE()

Greg Kroah-Hartman
2025-04-08T12:09:27Z

From: Roman Smirnov <r.smirnov@omp.ru>

commit a8dfb2168906944ea61acfc87846b816eeab882d upstream.

If the file system is corrupted, the header.stblindex variable
may become greater than 127. Because of this, an array access out
of bounds may occur:

------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dtree.c:3096:10
index 237 is out of range for type 'struct dtslot[128]'
CPU: 0 UID: 0 PID: 5822 Comm: syz-executor740 Not tainted 6.13.0-rc4-syzkaller-00110-g4099a71718b0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
ubsan_epilogue lib/ubsan.c:231 [inline]
__ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:429
dtReadFirst+0x622/0xc50 fs/jfs/jfs_dtree.c:3096
dtReadNext fs/jfs/jfs_dtree.c:3147 [inline]
jfs_readdir+0x9aa/0x3c50 fs/jfs/jfs_dtree.c:2862
wrap_directory_iterator+0x91/0xd0 fs/readdir.c:65
iterate_dir+0x571/0x800 fs/readdir.c:108
__do_sys_getdents64 fs/readdir.c:403 [inline]
__se_sys_getdents64+0x1e2/0x4b0 fs/readdir.c:389
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
</TASK>
---[ end trace ]---

Add a stblindex check for corruption.

Reported-by: syzbot <syzbot+9120834fc227768625ba@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=9120834fc227768625ba
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Roman Smirnov <r.smirnov@omp.ru>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/jfs/jfs_dtree.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/jfs/jfs_dtree.c
+++ b/fs/jfs/jfs_dtree.c
@@ -117,7 +117,8 @@ do { \
if (!(RC)) { \
if (((P)->header.nextindex > \
(((BN) == 0) ? DTROOTMAXSLOT : (P)->header.maxslot)) || \
- ((BN) && ((P)->header.maxslot > DTPAGEMAXSLOT))) { \
+ ((BN) && (((P)->header.maxslot > DTPAGEMAXSLOT) || \
+ ((P)->header.stblindex >= DTPAGEMAXSLOT)))) { \
BT_PUTPAGE(MP); \
jfs_error((IP)->i_sb, \
"DT_GETPAGE: dtree page corrupt\n"); \