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 A22BE39B947 for ; Sat, 28 Feb 2026 18:15:13 +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=1772302513; cv=none; b=V3Mc47Y1QLssOdWG0e07yU9bOOt83Ia+jLYd1Cg7NDoXO4bsS3eU/j+G8Jv6dY6kFQgTeMqBde89dQPlNQi3h3s1WjsLzesz/BxX2G8zGgS32p5T8A7Q/wRD3QzbY7kiuKJR25K7pk3yx2VUm89wRTW8iRUIySG0HbqkkvBQvQI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772302513; c=relaxed/simple; bh=/8VO0Oj4E5wLdPLzdIVMNTk4c/DfpjmHmm6nWhBM/bw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=f6WOr7rsbtRXCe+falGVj30Nz5YN/rzxUtBq4bWPvoW0aSmkLT2OuwpTyeDB4wvA79IKmvewp9rRjwBzzk8NDJgCFopAbbS784Of5gX9YQF/8x4FKrsgNuur8PwhInQUzak76EGsvW9wXVu1A6brNJK2+fD/gJWdbTBw1NFtvrY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Cnxmj9LG; 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="Cnxmj9LG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2856C19423; Sat, 28 Feb 2026 18:15:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772302513; bh=/8VO0Oj4E5wLdPLzdIVMNTk4c/DfpjmHmm6nWhBM/bw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Cnxmj9LGpKRpXFt7fmGzaG9epWDUbE4XD1477U9BQNAphUKZD45XagF2yky4dEDtO NWHGSxFiG0LNHfwGJlg0YMDh5+fRkykHvfpFPU6bJ0TTj3sSen2AcI9ZiDPEIRbKWh hR6ZQ39NMY5mJ9YkzGUhpVtL778SPaBDW6SJrWPjXrb24sjFjk1U+2V6ZvXXEHzGl1 mWCCl+o7Yr8XbRnMgh+cHPw93bapeS6Db0sLilPT8a9Ik2w7pV4SMk4JbJGY3OgudB P616x7ST5Y9U64XAsxTokAetdfdFrqSfo3lB1ruNfTUrzWXbAP5jfi5vCEnZnWrTu7 V3t6/JNjz+cRg== From: Sasha Levin To: patches@lists.linux.dev Cc: Deepanshu Kartikey , syzbot+ea1cd4aa4d1e98458a55@syzkaller.appspotmail.com, Andreas Gruenbacher , Sasha Levin Subject: [PATCH 5.15 009/164] gfs2: Fix use-after-free in iomap inline data write path Date: Sat, 28 Feb 2026 13:12:28 -0500 Message-ID: <20260228181505.1600663-9-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228181505.1600663-1-sashal@kernel.org> References: <20260228181505.1600663-1-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 7425c90e47eb5..1e95d777f6737 100644 --- a/fs/gfs2/bmap.c +++ b/fs/gfs2/bmap.c @@ -1114,10 +1114,18 @@ 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); @@ -1131,6 +1139,9 @@ 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