Commit d995417b authored by Ryusuke Konishi's avatar Ryusuke Konishi Committed by Zizhi Wo
Browse files

nilfs2: fix potential out-of-bounds memory access in nilfs_find_entry() 

stable inclusion
from stable-v5.4.287
commit 09d6d05579fd46e61abf6e457bb100ff11f3a9d3
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBEANS
CVE: CVE-2024-56619

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=09d6d05579fd46e61abf6e457bb100ff11f3a9d3

--------------------------------

commit 985ebec4ab0a28bb5910c3b1481a40fbf7f9e61d upstream.

Syzbot reported that when searching for records in a directory where the
inode's i_size is corrupted and has a large value, memory access outside
the folio/page range may occur, or a use-after-free bug may be detected if
KASAN is enabled.

This is because nilfs_last_byte(), which is called by nilfs_find_entry()
and others to calculate the number of valid bytes of directory data in a
page from i_size and the page index, loses the upper 32 bits of the 64-bit
size information due to an inappropriate type of local variable to which
the i_size value is assigned.

This caused a large byte offset value due to underflow in the end address
calculation in the calling nilfs_find_entry(), resulting in memory access
that exceeds the folio/page size.

Fix this issue by changing the type of the local variable causing the bit
loss from "unsigned int" to "u64".  The return value of nilfs_last_byte()
is also of type "unsigned int", but it is truncated so as not to exceed
PAGE_SIZE and no bit loss occurs, so no change is required.

Link: https://lkml.kernel.org/r/20241119172403.9292-1-konishi.ryusuke@gmail.com


Fixes: 2ba466d7 ("nilfs2: directory entry operations")
Signed-off-by: default avatarRyusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: default avatar <syzbot+96d5d14c47d97015c624@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=96d5d14c47d97015c624


Tested-by: default avatar <syzbot+96d5d14c47d97015c624@syzkaller.appspotmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarZizhi Wo <wozizhi@huawei.com>
parent 4c116feb

fs/nilfs2/dir.c

+1 −1
Original line number Diff line number Diff line
@@ -76,7 +76,7 @@ static inline void nilfs_put_page(struct page *page) 
 */

static unsigned int nilfs_last_byte(struct inode *inode, unsigned long page_nr)

{

	unsigned int last_byte = inode->i_size;

	u64 last_byte = inode->i_size;



	last_byte -= page_nr << PAGE_SHIFT;

	if (last_byte > PAGE_SIZE)