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 A025121D596; Wed, 25 Feb 2026 01:27:51 +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=1771982871; cv=none; b=br0Ka0JkZUIZtxKHylaTCPjDKHQto1dLUlGPI1ei8VCVhfBUZ6daZRL0Kmqgt6QG5XtltIoXpIMtDWdrZNjzN97P1VcvsSpdGJxEFFy+yz9FtDJlGbwYuTZHf5F5Cc2bxs5zv6VXvavB2rr1aEU5ftcgbGFoSfSUGDahyRFVKdw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771982871; c=relaxed/simple; bh=4AfeZLSwyCl/mNnkxLgnDVs0D0ZDOlydQLZDbZ/+2Mc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jJ1/bWLQ+V+7bD5D+0o5gbkKVKxKF7FyGfmclwFHHAXjf3oRIYnGgkvhas6H0bOI43b6HF2y8m4y/tOJxN5bNpusJi948gH4d19sOAnT7YsSFAK8l3wp9rLJuKQOXriEZo/eEMyHb9p30nMcC9yv9uZrZkeqjFxK8lAcIag8Rok= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CJrG3h0W; 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="CJrG3h0W" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F07CC19423; Wed, 25 Feb 2026 01:27:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1771982871; bh=4AfeZLSwyCl/mNnkxLgnDVs0D0ZDOlydQLZDbZ/+2Mc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CJrG3h0WJCoEbm9b8TPxuQE7SSTSC0iLQby0m1cCc9ZwHi7bbJOSie+34+sd/VB2d 3GLvoe4kSbegJs5aID0oQRpR2srhDEoeHuQsOVt1Ocms0D4+Yg29OsA5W+F1VoM9tm pF7bqEG5tESi3lKo74L4IVt6QT8KaXLmg5HguTfo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+ea1cd4aa4d1e98458a55@syzkaller.appspotmail.com, Deepanshu Kartikey , Andreas Gruenbacher , Sasha Levin Subject: [PATCH 6.19 021/781] gfs2: Fix use-after-free in iomap inline data write path Date: Tue, 24 Feb 2026 17:12:10 -0800 Message-ID: <20260225012400.222387762@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260225012359.695468795@linuxfoundation.org> References: <20260225012359.695468795@linuxfoundation.org> User-Agent: quilt/0.69 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 6.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Deepanshu Kartikey [ Upstream commit faddeb848305e79db89ee0479bb0e33380656321 ] The inline data buffer head (dibh) is being released prematurely in gfs2_iomap_begin() via release_metapath() while iomap->inline_data still points to dibh->b_data. This causes a use-after-free when iomap_write_end_inline() later attempts to write to the inline data area. The bug sequence: 1. gfs2_iomap_begin() calls gfs2_meta_inode_buffer() to read inode metadata into dibh 2. Sets iomap->inline_data = dibh->b_data + sizeof(struct gfs2_dinode) 3. Calls release_metapath() which calls brelse(dibh), dropping refcount to 0 4. kswapd reclaims the page (~39ms later in the syzbot report) 5. iomap_write_end_inline() tries to memcpy() to iomap->inline_data 6. KASAN detects use-after-free write to freed memory Fix by storing dibh in iomap->private and incrementing its refcount with get_bh() in gfs2_iomap_begin(). The buffer is then properly released in gfs2_iomap_end() after the inline write completes, ensuring the page stays alive for the entire iomap operation. Note: A C reproducer is not available for this issue. The fix is based on analysis of the KASAN report and code review showing the buffer head is freed before use. [agruenba: Take buffer head reference in gfs2_iomap_begin() to avoid leaks in gfs2_iomap_get() and gfs2_iomap_alloc().] Reported-by: syzbot+ea1cd4aa4d1e98458a55@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=ea1cd4aa4d1e98458a55 Fixes: d0a22a4b03b8 ("gfs2: Fix iomap write page reclaim deadlock") Signed-off-by: Deepanshu Kartikey Signed-off-by: Andreas Gruenbacher Signed-off-by: Sasha Levin --- fs/gfs2/bmap.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c index 131091520de6b..fdcac8e3f2ba2 100644 --- a/fs/gfs2/bmap.c +++ b/fs/gfs2/bmap.c @@ -1127,10 +1127,18 @@ static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length, goto out_unlock; break; default: - goto out_unlock; + goto out; } ret = gfs2_iomap_begin_write(inode, pos, length, flags, iomap, &mp); + if (ret) + goto out_unlock; + +out: + if (iomap->type == IOMAP_INLINE) { + iomap->private = metapath_dibh(&mp); + get_bh(iomap->private); + } out_unlock: release_metapath(&mp); @@ -1144,6 +1152,9 @@ static int gfs2_iomap_end(struct inode *inode, loff_t pos, loff_t length, struct gfs2_inode *ip = GFS2_I(inode); struct gfs2_sbd *sdp = GFS2_SB(inode); + if (iomap->private) + brelse(iomap->private); + switch (flags & (IOMAP_WRITE | IOMAP_ZERO)) { case IOMAP_WRITE: if (flags & IOMAP_DIRECT) -- 2.51.0