The patch titled
Subject: nilfs2: fix null-ptr-deref in block_touch_buffer tracepoint
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
nilfs2-fix-null-ptr-deref-in-block_touch_buffer-tracepoint.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-fix-null-ptr-deref-in-block_touch_buffer-tracepoint.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@xxxxxxxxx>
Subject: nilfs2: fix null-ptr-deref in block_touch_buffer tracepoint
Date: Thu, 7 Nov 2024 01:07:32 +0900
Patch series "nilfs2: fix null-ptr-deref bugs on block tracepoints".
This series fixes null pointer dereference bugs that occur when using
nilfs2 and two block-related tracepoints.
This patch (of 2):
It has been reported that when using "block:block_touch_buffer"
tracepoint, touch_buffer() called from __nilfs_get_folio_block() causes a
NULL pointer dereference, or a general protection fault when KASAN is
enabled.
This happens because since the tracepoint was added in touch_buffer(), it
references the dev_t member bh->b_bdev->bd_dev regardless of whether the
buffer head has a pointer to a block_device structure. In the current
implementation, the block_device structure is set after the function
returns to the caller.
Here, touch_buffer() is used to mark the folio/page that owns the buffer
head as accessed, but the common search helper for folio/page used by the
caller function was optimized to mark the folio/page as accessed when it
was reimplemented a long time ago, eliminating the need to call
touch_buffer() here in the first place.
So this solves the issue by eliminating the touch_buffer() call itself.
Link: https://lkml.kernel.org/r/20241106160811.3316-1-konishi.ryusuke@xxxxxxxxx
Link: https://lkml.kernel.org/r/20241106160811.3316-2-konishi.ryusuke@xxxxxxxxx
Fixes: 5305cb830834 ("block: add block_{touch|dirty}_buffer tracepoint")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Reported-by: Ubisectech Sirius <bugreport@xxxxxxxxxxxxxx>
Closes: https://lkml.kernel.org/r/86bd3013-887e-4e38-960f-ca45c657f032.bugreport@xxxxxxxxxxxxxx
Reported-by: syzbot+9982fb8d18eba905abe2@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=9982fb8d18eba905abe2
Tested-by: syzbot+9982fb8d18eba905abe2@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/page.c | 1 -
1 file changed, 1 deletion(-)
--- a/fs/nilfs2/page.c~nilfs2-fix-null-ptr-deref-in-block_touch_buffer-tracepoint
+++ a/fs/nilfs2/page.c
@@ -39,7 +39,6 @@ static struct buffer_head *__nilfs_get_f
first_block = (unsigned long)index << (PAGE_SHIFT - blkbits);
bh = get_nth_bh(bh, block - first_block);
- touch_buffer(bh);
wait_on_buffer(bh);
return bh;
}
_
Patches currently in -mm which might be from konishi.ryusuke@xxxxxxxxx are
nilfs2-fix-null-ptr-deref-in-block_touch_buffer-tracepoint.patch
nilfs2-fix-null-ptr-deref-in-block_dirty_buffer-tracepoint.patch
