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...
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