[syzbot] [jfs?] UBSAN: array-index-out-of-bounds in dtReadFirst

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5eb4573ea63d Merge tag 'soc-fixes-6.9-2' of git://git.kern..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10d00af8980000
kernel config: https://syzkaller.appspot.com/x/.config?x=3d46aa9d7a44f40d
dashboard link: https://syzkaller.appspot.com/bug?extid=65fa06e29859e41a83f3
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=103728a7180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b3c937180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7e4c1378cbb1/disk-5eb4573e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8e4487ecdd86/vmlinux-5eb4573e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d84518ee028f/bzImage-5eb4573e.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/8d252f0d561d/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+65fa06...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dtree.c:3087:20
index -1 is out of range for type 'struct dtslot[128]'
CPU: 0 PID: 5074 Comm: syz-executor356 Not tainted 6.9.0-rc5-syzkaller-00296-g5eb4573ea63d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
ubsan_epilogue lib/ubsan.c:231 [inline]
__ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:429
dtReadFirst+0x612/0xbe0 fs/jfs/jfs_dtree.c:3087
jfs_readdir+0x81a/0x4660 fs/jfs/jfs_dtree.c:2818
wrap_directory_iterator+0x94/0xe0 fs/readdir.c:67
iterate_dir+0x539/0x6f0 fs/readdir.c:110
__do_sys_getdents64 fs/readdir.c:409 [inline]
__se_sys_getdents64+0x20d/0x4f0 fs/readdir.c:394
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3471781639
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcff008118 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007ffcff0082e8 RCX: 00007f3471781639
RDX: 0000000000001000 RSI: 0000000020002ec0 RDI: 0000000000000005
RBP: 00007f34717fa610 R08: 0000000000000000 R09: 00007ffcff0082e8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffcff0082d8 R14: 0000000000000001 R15: 0000000000000001
</TASK>
---[ end trace ]---


---
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[Edward Adam Davis]

please test oob in dtReadFirst

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 5eb4573ea63d

diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c
index 5d3127ca68a4..f5d5467a49e6 100644
--- a/fs/jfs/jfs_dtree.c
+++ b/fs/jfs/jfs_dtree.c
@@ -3086,6 +3086,11 @@ static int dtReadFirst(struct inode *ip, struct btstack * btstack)

/* get the leftmost entry */
stbl = DT_GETSTBL(p);
+ if (stbl[0] < 0 || stbl[0] > 127) {
+ DT_PUTPAGE(mp);
+ jfs_error(ip->i_sb, "stbl[0] out of bound\n");
+ return -EIO;
+ }
xd = (pxd_t *) & p->slot[stbl[0]];

/* get the child page block address */

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+65fa06...@syzkaller.appspotmail.com

Tested on:

commit: 5eb4573e Merge tag 'soc-fixes-6.9-2' of git://git.kern..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=145680d4980000

kernel config: https://syzkaller.appspot.com/x/.config?x=3d46aa9d7a44f40d
dashboard link: https://syzkaller.appspot.com/bug?extid=65fa06e29859e41a83f3
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=12c6d86c980000

Note: testing is done by a robot and is best-effort only.