+ nilfs2-fix-potential-out-of-bounds-memory-access-in-nilfs_find_entry.patch added to mm-hotfixes-unstable branch

+ nilfs2-fix-potential-out-of-bounds-memory-access-in-nilfs_find_entry.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: nilfs2: fix potential out-of-bounds memory access in nilfs_find_entry()
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     nilfs2-fix-potential-out-of-bounds-memory-access-in-nilfs_find_entry.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-fix-potential-out-of-bounds-memory-access-in-nilfs_find_entry.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Subject: nilfs2: fix potential out-of-bounds memory access in nilfs_find_entry()
Date: Wed, 20 Nov 2024 02:23:37 +0900

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: 2ba466d74ed7 ("nilfs2: directory entry operations")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+96d5d14c47d97015c624@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=96d5d14c47d97015c624
Tested-by: syzbot+96d5d14c47d97015c624@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/nilfs2/dir.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/nilfs2/dir.c~nilfs2-fix-potential-out-of-bounds-memory-access-in-nilfs_find_entry
+++ a/fs/nilfs2/dir.c
@@ -70,7 +70,7 @@ static inline unsigned int nilfs_chunk_s
  */
 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)
_

Patches currently in -mm which might be from konishi.ryusuke@gmail.com are

nilfs2-fix-potential-out-of-bounds-memory-access-in-nilfs_find_entry.patch