From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1D88622424C for ; Tue, 17 Feb 2026 15:19:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771341599; cv=none; b=QRsYS7NnegENXm9otnz2LFh34pKsBjeg0xQPRPsIrOctUboP5Th9kdfE7BpUPtG0zPk53+jguUKWJNPBeQdX3cUI9q31mTfsC41cnU5dVBprJDX9GByShuROZFXKyx3xD9IVsIJWF+NJA4uHqv/T4laPUFSPfxSoiDqGQ0/G+Bg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771341599; c=relaxed/simple; bh=0qu+xXrRXaZ5NprmhEkOBj0+pYsBwMTR6Qbu5PZSi7Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ktQoYOZscqdEi7Z1YABMTpkodhImLjPQ6bodx1hA0x7ncV0fFOp/9Sql0MHCqp+VHRdMLvK6K2LNF+dfuKskkUq0NlWdSXXb+an641f9sN/XphS8AZEZpH0mcEK1i6yPaLS4qzKTV9MLQlXNDHSlCKxOZGNtpt68U5aKfvpt7yY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XwQ1cu7O; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XwQ1cu7O" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02B34C4CEF7; Tue, 17 Feb 2026 15:19:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771341598; bh=0qu+xXrRXaZ5NprmhEkOBj0+pYsBwMTR6Qbu5PZSi7Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XwQ1cu7OShY1iVO0zCXU1xlz3jT1t+CFUKkgCaReESM7zNbjifZwO9cEbELxihVTB kGgBPD+zx+SwL7aEZXTveEOs6RRnOiknd4oCW46LpZeMn7rSvPmxdh0EEtc7ULjV+Z PdcL+7ERXc96o6dsLOK+yXr44b3+AEdRyB5LB0AG/otTapB8YgWnSBoehPFbdsKw4j WP0tD/LUFyvzCSDHMZxLGtCzjgju+WnGz/cDmQWsk8Oy7zHDkAvMFvGIVZshBjbz8P hNpYGUUpamfGMtI/O4hVZeMKJET2fgr9s5D7r3dmqIZqWE0fd8w3PScSYMEGBNOLOl PPa74nrThbQ2g== From: Sasha Levin To: stable@vger.kernel.org Cc: Chao Yu , stable@kernel.org, syzbot+b4444e3c972a7a124187@syzkaller.appspotmail.com, Jaegeuk Kim , Sasha Levin Subject: [PATCH 6.12.y] f2fs: fix to avoid UAF in f2fs_write_end_io() Date: Tue, 17 Feb 2026 10:19:55 -0500 Message-ID: <20260217151955.3678030-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2026021708-pellet-surname-cfb8@gregkh> References: <2026021708-pellet-surname-cfb8@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chao Yu [ Upstream commit ce2739e482bce8d2c014d76c4531c877f382aa54 ] As syzbot reported an use-after-free issue in f2fs_write_end_io(). It is caused by below race condition: loop device umount - worker_thread - loop_process_work - do_req_filebacked - lo_rw_aio - lo_rw_aio_complete - blk_mq_end_request - blk_update_request - f2fs_write_end_io - dec_page_count - folio_end_writeback - kill_f2fs_super - kill_block_super - f2fs_put_super : free(sbi) : get_pages(, F2FS_WB_CP_DATA) accessed sbi which is freed In kill_f2fs_super(), we will drop all page caches of f2fs inodes before call free(sbi), it guarantee that all folios should end its writeback, so it should be safe to access sbi before last folio_end_writeback(). Let's relocate ckpt thread wakeup flow before folio_end_writeback() to resolve this issue. Cc: stable@kernel.org Fixes: e234088758fc ("f2fs: avoid wait if IO end up when do_checkpoint for better performance") Reported-by: syzbot+b4444e3c972a7a124187@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b4444e3c972a7a124187 Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim [ folio => page ] Signed-off-by: Sasha Levin --- fs/f2fs/data.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index ea831671e3ad2..fb3ef2d211591 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -357,14 +357,20 @@ static void f2fs_write_end_io(struct bio *bio) page_folio(page)->index != nid_of_node(page)); dec_page_count(sbi, type); + + /* + * we should access sbi before end_page_writeback() to + * avoid racing w/ kill_f2fs_super() + */ + if (type == F2FS_WB_CP_DATA && !get_pages(sbi, type) && + wq_has_sleeper(&sbi->cp_wait)) + wake_up(&sbi->cp_wait); + if (f2fs_in_warm_node_list(sbi, page)) f2fs_del_fsync_node_entry(sbi, page); clear_page_private_gcing(page); end_page_writeback(page); } - if (!get_pages(sbi, F2FS_WB_CP_DATA) && - wq_has_sleeper(&sbi->cp_wait)) - wake_up(&sbi->cp_wait); bio_put(bio); } -- 2.51.0