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 4BE9117A2E8; Mon, 10 Mar 2025 18:02:16 +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=1741629736; cv=none; b=JjcqmqU/2meDjgf9J+al1rYEszxpXN3h7xq/YGymXZo1TtcSsJQ+MWn97k/YxF4j8ec+oTdTcO75dDe39f8QhHsIj8Mc5xeZ6e5gr8kgblWyZ7aVg5LdXl7xc1gzV43khPYTF8M3uHhs0MvU/SDT06reDWKlsstKpoIi/Sm1AGE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741629736; c=relaxed/simple; bh=QVKeZ2q/2+JxQrEn0NcpRe1IW7RdkBRZme+GyJO61iA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aniQ+rwwaYJbeGchDanU3YZusKg67OLTr+Xy46mtzAzg1KRxjmGceuinLJognRJDk3fX7TUfI3dScCxOw8zPjOU8tWkdUnumPmQrKaxav10zm00kWG78vUC+z6HOBpYZOw6rvbb7faxIdqfs0Z/Ri4jEjtvfzPPfb/FANfyAtmg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SLiO7q5v; 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="SLiO7q5v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE4B7C4CEE5; Mon, 10 Mar 2025 18:02:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1741629736; bh=QVKeZ2q/2+JxQrEn0NcpRe1IW7RdkBRZme+GyJO61iA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SLiO7q5vRoL7Bt7XVzlqsmS8KqpwEs9Gndm+kVA1fjwET8YUwdYC/+5L2VDtw0CrJ z9zMwLqHcNiF4Qsc99+ANdsdvfuzc8oTNELVPUOUyDIW9Oczgdp4TNOMw44lTdiwOv svRH3cv6Ce/S5selkt9JjsokeT25Um3AcUH8f2B0= 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 5.15 388/620] btrfs: fix hole expansion when writing at an offset beyond EOF Date: Mon, 10 Mar 2025 18:03:54 +0100 Message-ID: <20250310170600.912025287@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250310170545.553361750@linuxfoundation.org> References: <20250310170545.553361750@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-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 @@ -1607,7 +1607,6 @@ static int btrfs_write_check(struct kioc loff_t pos = iocb->ki_pos; int ret; loff_t oldsize; - loff_t start_pos; if (iocb->ki_flags & IOCB_NOWAIT) { size_t nocow_bytes = count; @@ -1637,9 +1636,8 @@ static int btrfs_write_check(struct kioc */ 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);