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 96DFD1E1C0F; Wed, 19 Feb 2025 09:31:02 +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=1739957462; cv=none; b=F2KaOF4WJ4ec0iWsxaCJXAvZxjr10mzF/NjBm1TroFCUfN0ILmrEn2OcIcl/avizRGjQ6F4BYhbtrrCDBFoS4ByWLmuBmXrULtZBj8Yc0/lEWC/ljywrCh2FmT7YC3Mh3e5vtoTRK46t9ecXPpV4W8pzAaEguaXemwb/FYW6paY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739957462; c=relaxed/simple; bh=PV1+7TzcW/IS25Rb0hkIXsBcrTFGMwA+nIz5a/CDsqY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=loXTi5kWIhDBzrfbBd6k5vOyfztaVzMLCH/8kCBVvAFIs6hC5TVdyrXYC5A89gbuVrJpk69q8lwSfGWJ1hbcVzoKrHDJRxYVSYeXsQ5+H/AyT1vdBA/MUsI1anTsRZ0U0u/w+tiImNojua0VlqV4C4biLz49O4tbhlCATfYra+k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cbPv2ehH; 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="cbPv2ehH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F3C2C4CED1; Wed, 19 Feb 2025 09:31:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1739957462; bh=PV1+7TzcW/IS25Rb0hkIXsBcrTFGMwA+nIz5a/CDsqY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cbPv2ehH9lk0xzrXjoyPHzjdSTNuBohUU8zhJ/EBLingZJLsBLvZlOCPYdS/AN2JN 5k118ojdiViJpii4GUOAl4jBIiOJ5gAMnrepWvDc18lXpJWsPFT5DqaKbrgCj5CYB6 A+iz+9VK4p97WEUTO+GgWm2EIRwZI9VeeIvXSS2c= 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 6.1 535/578] btrfs: fix hole expansion when writing at an offset beyond EOF Date: Wed, 19 Feb 2025 09:28:59 +0100 Message-ID: <20250219082714.022429500@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250219082652.891560343@linuxfoundation.org> References: <20250219082652.891560343@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 6.1-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 @@ -1122,7 +1122,6 @@ static int btrfs_write_check(struct kioc 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 @@ -1147,9 +1146,8 @@ 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);