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

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Message-ID: <ab28ec2e-3576-4f7c-9157-9933b1fada89@oracle.com>
Date: Wed, 19 Feb 2025 16:52:42 -0600
From: Dave Kleikamp <dave.kleikamp@...cle.com>
To: Zhongqiu Han <quic_zhonhan@...cinc.com>, aha310510@...il.com
Cc: jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        syzbot+df6cdcb35904203d2b6d@...kaller.appspotmail.com
Subject: Re: [PATCH] jfs: Fix uninit-value access of imap allocated in the
 diMount() function

On 2/19/25 8:02AM, Zhongqiu Han wrote:
> 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().

Looks good. I'll add it to jfs-next.

> 
> 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;
>