linux-kernel - [PATCH] fs/ntfs3: Fix slab-out-of-bounds read in ntfs_trim

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Date:   Sat,  1 Oct 2022 12:30:24 +0530
From:   Abdun Nihaal <abdun.nihaal@...il.com>
To:     almaz.alexandrovich@...agon-software.com
Cc:     ntfs3@...ts.linux.dev, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Abdun Nihaal <abdun.nihaal@...il.com>,
        syzbot+b892240eac461e488d51@...kaller.appspotmail.com
Subject: [PATCH] fs/ntfs3: Fix slab-out-of-bounds read in ntfs_trim_fs

Syzbot reports an out of bound access in ntfs_trim_fs.
The cause of this is using a loop termination condition that compares
window index (iw) with wnd->nbits instead of wnd->nwnd, due to which the
index used for wnd->free_bits exceeds the size of the array allocated.

Fix the loop condition.

Fixes: 3f3b442b5ad2 ("fs/ntfs3: Add bitmap")
Link: https://syzkaller.appspot.com/bug?extid=b892240eac461e488d51
Reported-by: syzbot+b892240eac461e488d51@...kaller.appspotmail.com
Signed-off-by: Abdun Nihaal <abdun.nihaal@...il.com>
---
 fs/ntfs3/bitmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ntfs3/bitmap.c b/fs/ntfs3/bitmap.c
index 1675c9a69788..629c1ee97268 100644
--- a/fs/ntfs3/bitmap.c
+++ b/fs/ntfs3/bitmap.c
@@ -1424,7 +1424,7 @@ int ntfs_trim_fs(struct ntfs_sb_info *sbi, struct fstrim_range *range)
 
 	down_read_nested(&wnd->rw_lock, BITMAP_MUTEX_CLUSTERS);
 
-	for (; iw < wnd->nbits; iw++, wbit = 0) {
+	for (; iw < wnd->nwnd; iw++, wbit = 0) {
 		CLST lcn_wnd = iw * wbits;
 		struct buffer_head *bh;
 
-- 
2.37.3