linux-kernel - [PATCH] jfs: Fix uninit-value access of imap allocated in the diMount() function

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Message-ID: <20250219140211.3912351-1-quic_zhonhan@quicinc.com>
Date: Wed, 19 Feb 2025 22:02:11 +0800
From: Zhongqiu Han <quic_zhonhan@...cinc.com>
To: <shaggy@...nel.org>, <aha310510@...il.com>
CC: <jfs-discussion@...ts.sourceforge.net>, <linux-kernel@...r.kernel.org>,
        <quic_zhonhan@...cinc.com>,
        <syzbot+df6cdcb35904203d2b6d@...kaller.appspotmail.com>
Subject: [PATCH] jfs: Fix uninit-value access of imap allocated in the diMount() function

syzbot reports that hex_dump_to_buffer is using uninit-value:

=====================================================
BUG: KMSAN: uninit-value in hex_dump_to_buffer+0x888/0x1100 lib/hexdump.c:171
hex_dump_to_buffer+0x888/0x1100 lib/hexdump.c:171
print_hex_dump+0x13d/0x3e0 lib/hexdump.c:276
diFree+0x5ba/0x4350 fs/jfs/jfs_imap.c:876
jfs_evict_inode+0x510/0x550 fs/jfs/inode.c:156
evict+0x723/0xd10 fs/inode.c:796
iput_final fs/inode.c:1946 [inline]
iput+0x97b/0xdb0 fs/inode.c:1972
txUpdateMap+0xf3e/0x1150 fs/jfs/jfs_txnmgr.c:2367
txLazyCommit fs/jfs/jfs_txnmgr.c:2664 [inline]
jfs_lazycommit+0x627/0x11d0 fs/jfs/jfs_txnmgr.c:2733
kthread+0x6b9/0xef0 kernel/kthread.c:464
ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was created at:
slab_post_alloc_hook mm/slub.c:4121 [inline]
slab_alloc_node mm/slub.c:4164 [inline]
__kmalloc_cache_noprof+0x8e3/0xdf0 mm/slub.c:4320
kmalloc_noprof include/linux/slab.h:901 [inline]
diMount+0x61/0x7f0 fs/jfs/jfs_imap.c:105
jfs_mount+0xa8e/0x11d0 fs/jfs/jfs_mount.c:176
jfs_fill_super+0xa47/0x17c0 fs/jfs/super.c:523
get_tree_bdev_flags+0x6ec/0x910 fs/super.c:1636
get_tree_bdev+0x37/0x50 fs/super.c:1659
jfs_get_tree+0x34/0x40 fs/jfs/super.c:635
vfs_get_tree+0xb1/0x5a0 fs/super.c:1814
do_new_mount+0x71f/0x15e0 fs/namespace.c:3560
path_mount+0x742/0x1f10 fs/namespace.c:3887
do_mount fs/namespace.c:3900 [inline]
__do_sys_mount fs/namespace.c:4111 [inline]
__se_sys_mount+0x71f/0x800 fs/namespace.c:4088
__x64_sys_mount+0xe4/0x150 fs/namespace.c:4088
x64_sys_call+0x39bf/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
=====================================================

The reason is that imap is not properly initialized after memory
allocation. It will cause the snprintf() function to write uninitialized
data into linebuf within hex_dump_to_buffer().

Fix this by using kzalloc instead of kmalloc to clear its content at the
beginning in diMount().

Signed-off-by: Zhongqiu Han <quic_zhonhan@...cinc.com>
Reported-by: syzbot+df6cdcb35904203d2b6d@...kaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/67b5d07e.050a0220.14d86d.00e6.GAE@google.com/
---
 fs/jfs/jfs_imap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index a360b24ed320..cf16655cd26b 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -102,7 +102,7 @@ int diMount(struct inode *ipimap)
 	 * allocate/initialize the in-memory inode map control structure
 	 */
 	/* allocate the in-memory inode map control structure. */
-	imap = kmalloc(sizeof(struct inomap), GFP_KERNEL);
+	imap = kzalloc(sizeof(struct inomap), GFP_KERNEL);
 	if (imap == NULL)
 		return -ENOMEM;
 
-- 
2.25.1