linux-kernel - [PATCH] jfs: add index corruption check to DT

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Message-ID: <20250226082523.112081-1-r.smirnov@omp.ru>
Date: Wed, 26 Feb 2025 11:25:22 +0300
From: Roman Smirnov <r.smirnov@....ru>
To: Dave Kleikamp <shaggy@...nel.org>
CC: Roman Smirnov <r.smirnov@....ru>, Ghanshyam Agrawal
	<ghanshyam1898@...il.com>, Edward Adam Davis <eadavis@...com>,
	<jfs-discussion@...ts.sourceforge.net>, <linux-kernel@...r.kernel.org>,
	<lvc-project@...uxtesting.org>, syzbot
	<syzbot+9120834fc227768625ba@...kaller.appspotmail.com>,
	<stable@...r.kernel.org>
Subject: [PATCH] jfs: add index corruption check to DT_GETPAGE()

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@...kaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=9120834fc227768625ba
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@...r.kernel.org
Signed-off-by: Roman Smirnov <r.smirnov@....ru>
---
 fs/jfs/jfs_dtree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c
index 8f85177f284b..93db6eec4465 100644
--- 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");	\
-- 
2.34.1