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[60.34.120.249]) by smtp.gmail.com with ESMTPSA id d17-20020aa78151000000b0068675835e10sm3166507pfn.44.2023.08.05.06.20.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 05 Aug 2023 06:20:42 -0700 (PDT) From: Ryusuke Konishi To: Andrew Morton Cc: linux-nilfs@vger.kernel.org, syzbot , syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH] nilfs2: fix general protection fault in nilfs_lookup_dirty_data_buffers() Date: Sat, 5 Aug 2023 22:20:38 +0900 Message-Id: <20230805132038.6435-1-konishi.ryusuke@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <0000000000002930a705fc32b231@google.com> References: <0000000000002930a705fc32b231@google.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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. Signed-off-by: Ryusuke Konishi Reported-by: syzbot+0ad741797f4565e7e2d2@syzkaller.appspotmail.com Closes: https://lkml.kernel.org/r/0000000000002930a705fc32b231@google.com Tested-by: Ryusuke Konishi Cc: --- fs/nilfs2/segment.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c index 581691e4be49..7ec16879756e 100644 --- a/fs/nilfs2/segment.c +++ b/fs/nilfs2/segment.c @@ -725,6 +725,11 @@ static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode, 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);