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 9244A33507A for ; Sat, 28 Feb 2026 18:07:23 +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=1772302043; cv=none; b=A6fuyrjquU4BLaTlCnAzzCHiEEiApvj1q54SI0MwD5nX4HCIP02KzibClj0H7FFdC9odtHXn71S4vRRZu42VhZLSsk5iWcd5W30bG5S+40txIYG23l0OhTWqCN2JSfkHbyyIYRSIX0H/kUV/zd+bnBTWtp27jH2uVYIlKhY6cCQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772302043; c=relaxed/simple; bh=E3DhuYhjpDxXlg+XuGuEnyV4LZjyUyN0cl6sz5bb+mo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qCboA+MwgkjPAt7fZUFsRSFh8/HEAlxrd1PRiNR0KyW1m0EMGyOeNteTv3f/x3ir6iHjtDxVsd4Dq7xVn5POy4uKxuFVCMdmh2YQN3QNzUZnV9qUclBx4Y8oClryZhijBQflzKuen4R9l9lJJAsH5RXn/dzbiYcllCH5GniTvjk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xpr4fwPG; 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="Xpr4fwPG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE345C19423; Sat, 28 Feb 2026 18:07:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772302043; bh=E3DhuYhjpDxXlg+XuGuEnyV4LZjyUyN0cl6sz5bb+mo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Xpr4fwPGnXnWCczO2Abf6E8hFOvlR8ULTSJXZZmEsm1WWA1F+lswJ8V9YJ/I19YAY NivelI03k0LuMYap/YOkDorr2VPvm+OlbQKfr8mKuegtqu5haOe5C+LMh4NCzLoYv3 y/w+LTxal/VSWbDgnMDVaGbRV8OFz4rGCBlfoAqUY9GvFEqRitcYZD5533DBibbKkO VuCGhuOrmyGJ2VMDXWB0130vB2e1WRKj8MZ0im5GQLxLi6BgUL6lNdMDdgw+wXUWDC g+GHwzPynuOj3BEvFJkrMmu9ivnAEYWVthhZw8E570tDGYVHJI3NPDlbo27DURL/9Z PcEAV5ptEqd+A== From: Sasha Levin To: patches@lists.linux.dev Cc: Deepanshu Kartikey , syzbot+ea1cd4aa4d1e98458a55@syzkaller.appspotmail.com, Andreas Gruenbacher , Sasha Levin Subject: [PATCH 6.6 016/283] gfs2: Fix use-after-free in iomap inline data write path Date: Sat, 28 Feb 2026 13:02:38 -0500 Message-ID: <20260228180709.1583486-16-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228180709.1583486-1-sashal@kernel.org> References: <20260228180709.1583486-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit 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 b837a2c2dd571..bc0f7023adcf3 100644 --- a/fs/gfs2/bmap.c +++ b/fs/gfs2/bmap.c @@ -1126,10 +1126,18 @@ 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); @@ -1143,6 +1151,9 @@ 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