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 4C9581E8855; Wed, 19 Feb 2025 08:55:35 +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=1739955335; cv=none; b=aDhtzfEbqyn0GQNNI4AdRG9SVPt/wK/CcUL9L3YrRyXWDWwogQUuK16rVL/YW2Falpm+Sm+G2yD/2a7ZexLWbtSihP50v48n0G/TJzdaFEL0FyGkzT+w0iHh/mjtpTZqSJHcDiMMTYxrm0al6+y5f5wwZAUl9cfdeAKTJILRHV8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739955335; c=relaxed/simple; bh=E9SmRarCItTobkmH/rVe15gX1XCq55z8ceOX59Bw37E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Vat43BWliv87bqMoTEr9jMfKOs0QJ9vtrVR+HX8dp6F0nkXfYgcNYqCFOHacvOSsxVcCYrZchljE3yT1G/UpsFtiCvJ9av37ITkkV/awh6gz3SFUtiSB1Yye1yfWvoBGInGl9U6Z++zFZRgNuxKZ/Wewi05SlJxjDRzjTvBFN5M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TepUrBpD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="TepUrBpD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C1AE9C4CED1; Wed, 19 Feb 2025 08:55:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1739955335; bh=E9SmRarCItTobkmH/rVe15gX1XCq55z8ceOX59Bw37E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TepUrBpDFoLxAEFsZMLXjZQ0YGaQlubOU/49YKbXglBeoNff2yg838K5L1YWUhK9i BenFAWGNvYdg+B4zzpqJ4bWj0jL5ry5r8n2JdWm0l2GC4mEewp370ofyq67sqPZv+V AI5vgq9gZni1Fv+SWpe7GNzW7uIGx0tLqc6kR00w= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Qu Wenruo , Filipe Manana , David Sterba Subject: [PATCH 6.12 162/230] btrfs: fix hole expansion when writing at an offset beyond EOF Date: Wed, 19 Feb 2025 09:27:59 +0100 Message-ID: <20250219082608.033803132@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250219082601.683263930@linuxfoundation.org> References: <20250219082601.683263930@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Filipe Manana commit da2dccd7451de62b175fb8f0808d644959e964c7 upstream. At btrfs_write_check() if our file's i_size is not sector size aligned and we have a write that starts at an offset larger than the i_size that falls within the same page of the i_size, then we end up not zeroing the file range [i_size, write_offset). The code is this: start_pos = round_down(pos, fs_info->sectorsize); oldsize = i_size_read(inode); if (start_pos > oldsize) { /* Expand hole size to cover write data, preventing empty gap */ loff_t end_pos = round_up(pos + count, fs_info->sectorsize); ret = btrfs_cont_expand(BTRFS_I(inode), oldsize, end_pos); if (ret) return ret; } So if our file's i_size is 90269 bytes and a write at offset 90365 bytes comes in, we get 'start_pos' set to 90112 bytes, which is less than the i_size and therefore we don't zero out the range [90269, 90365) by calling btrfs_cont_expand(). This is an old bug introduced in commit 9036c10208e1 ("Btrfs: update hole handling v2"), from 2008, and the buggy code got moved around over the years. Fix this by discarding 'start_pos' and comparing against the write offset ('pos') without any alignment. This bug was recently exposed by test case generic/363 which tests this scenario by polluting ranges beyond EOF with an mmap write and than verify that after a file increases we get zeroes for the range which is supposed to be a hole and not what we wrote with the previous mmaped write. We're only seeing this exposed now because generic/363 used to run only on xfs until last Sunday's fstests update. The test was failing like this: $ ./check generic/363 FSTYP -- btrfs PLATFORM -- Linux/x86_64 debian0 6.13.0-rc7-btrfs-next-185+ #17 SMP PREEMPT_DYNAMIC Mon Feb 3 12:28:46 WET 2025 MKFS_OPTIONS -- /dev/sdc MOUNT_OPTIONS -- /dev/sdc /home/fdmanana/btrfs-tests/scratch_1 generic/363 0s ... [failed, exit status 1]- output mismatch (see /home/fdmanana/git/hub/xfstests/results//generic/363.out.bad) # --- tests/generic/363.out 2025-02-05 15:31:14.013646509 +0000 # +++ /home/fdmanana/git/hub/xfstests/results//generic/363.out.bad 2025-02-05 17:25:33.112630781 +0000 @@ -1 +1,46 @@ QA output created by 363 +READ BAD DATA: offset = 0xdcad, size = 0xd921, fname = /home/fdmanana/btrfs-tests/dev/junk +OFFSET GOOD BAD RANGE +0x1609d 0x0000 0x3104 0x0 +operation# (mod 256) for the bad data may be 4 +0x1609e 0x0000 0x0472 0x1 +operation# (mod 256) for the bad data may be 4 ... (Run 'diff -u /home/fdmanana/git/hub/xfstests/tests/generic/363.out /home/fdmanana/git/hub/xfstests/results//generic/363.out.bad' to see the entire diff) Ran: generic/363 Failures: generic/363 Failed 1 of 1 tests Fixes: 9036c10208e1 ("Btrfs: update hole handling v2") CC: stable@vger.kernel.org Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/file.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1148,7 +1148,6 @@ int btrfs_write_check(struct kiocb *iocb loff_t pos = iocb->ki_pos; int ret; loff_t oldsize; - loff_t start_pos; /* * Quickly bail out on NOWAIT writes if we don't have the nodatacow or @@ -1172,9 +1171,8 @@ int btrfs_write_check(struct kiocb *iocb */ update_time_for_write(inode); - start_pos = round_down(pos, fs_info->sectorsize); oldsize = i_size_read(inode); - if (start_pos > oldsize) { + if (pos > oldsize) { /* Expand hole size to cover write data, preventing empty gap */ loff_t end_pos = round_up(pos + count, fs_info->sectorsize);