The patch titled
Subject: nilfs2: fix general protection fault in nilfs_lookup_dirty_data_buffers()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
nilfs2-fix-general-protection-fault-in-nilfs_lookup_dirty_data_buffers.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-fix-general-protection-fault-in-nilfs_lookup_dirty_data_buffers.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 general protection fault in nilfs_lookup_dirty_data_buffers()
Date: Sat, 5 Aug 2023 22:20:38 +0900
A syzbot stress test reported that create_empty_buffers() called from
nilfs_lookup_dirty_data_buffers() can cause a general protection fault.
Analysis using its reproducer revealed that the back reference "mapping"
from a page/folio has been changed to NULL after dirty page/folio gang
lookup in nilfs_lookup_dirty_data_buffers().
Fix this issue by excluding pages/folios from being collected if, after
acquiring a lock on each page/folio, its back reference "mapping" differs
from the pointer to the address space struct that held the page/folio.
Link: https://lkml.kernel.org/r/20230805132038.6435-1-konishi.ryusuke@xxxxxxxxx
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Reported-by: syzbot+0ad741797f4565e7e2d2@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lkml.kernel.org/r/0000000000002930a705fc32b231@xxxxxxxxxx
Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/segment.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/fs/nilfs2/segment.c~nilfs2-fix-general-protection-fault-in-nilfs_lookup_dirty_data_buffers
+++ a/fs/nilfs2/segment.c
@@ -725,6 +725,11 @@ static size_t nilfs_lookup_dirty_data_bu
struct folio *folio = fbatch.folios[i];
folio_lock(folio);
+ if (unlikely(folio->mapping != mapping)) {
+ /* Exclude folios removed from the address space */
+ folio_unlock(folio);
+ continue;
+ }
head = folio_buffers(folio);
if (!head) {
create_empty_buffers(&folio->page, i_blocksize(inode), 0);
_
Patches currently in -mm which might be from konishi.ryusuke@xxxxxxxxx are
nilfs2-fix-general-protection-fault-in-nilfs_lookup_dirty_data_buffers.patch
