From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 B723C18D636; Fri, 4 Sep 2026 05:53:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501239; cv=none; b=TFtERInQvBjRW1rm/ECewhsGmQoVHr7irIdku7lGk1ukRQeSXe3dWyx9cita1LlVE3GUYIxst9/k39JI29FjUpX8lNkQq6PaCeqruK2s8dTOFXDAhh4kn4CHwym47zcdgOUW+bPIu1mmaagpX1lUu/Cbh+od2ojE0oTlEAo+gBo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501239; c=relaxed/simple; bh=epCWJ5zmLs8ezW18xnjPbX9L/cZbl5Egr4OAOtp6HJE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NLriTzVXeuo4GG3DVPnWC4KiAvRjgNlpcyI5zWGIg9bvutWmQMzuHaqKZxoIEr9aWWYdim+Lj2lI2Qoyqa8GrXHbXDa6T145WeJOE7i9ROULsYr9fbwcHzQvTOMi9mfhx2ernImSd2YB/sxuSbluqMR/DIXgCtHmASbEUc98++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=YojlbPwx; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="YojlbPwx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 240001F00A3D; Fri, 4 Sep 2026 05:53:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788501237; bh=ek7F27TuZGBKorXnsdRCVbiym7FGSmuIxXhtRp6Pje8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=YojlbPwxUgKXHM5NIA32KNx2SKxjeJ+XKVF+DBq0GUKRv683ag3RfvnHFViUGvL3z pyeqQTXCiYhD0DVcsGi2Oa4LkxkmCggluvooF+xA1W+vW1SqPQPZDM3MQSWye1HL9S Ac2RJfTF8WM8ecrteWD8K3mmbWwrfhJlKWD79q/I= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ibrahim Hashimov , Joseph Qi , Mark Fasheh , Joel Becker , Junxiao Bi , Changwei Ge , Jun Piao , Heming Zhao , Andrew Morton Subject: [PATCH 6.18 338/552] ocfs2: validate rl_used against rl_count in refcount block validator Date: Fri, 4 Sep 2026 06:58:15 +0200 Message-ID: <20260904045757.921842663@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ibrahim Hashimov commit 4ca62df6bc0708947b48da3f6a712ecb8e73929c upstream. ocfs2_find_refcount_rec_in_rl() walks the on-disk refcount record array with: for (; i < le16_to_cpu(rb->rf_records.rl_used); i++) { rec = &rb->rf_records.rl_recs[i]; ... rl_recs[] lives in a single metadata block (4096 bytes on the common configuration), so its real capacity is fixed by ocfs2_refcount_recs_per_rb(sb) (247 records for a 4K block with the 16-byte ocfs2_refcount_rec). rl_used and rl_count are both read directly off disk by ocfs2_validate_refcount_block() and are never checked against that capacity, nor against each other, before any refcount/reflink/CoW operation walks the array. A crafted (or corrupted) refcount block with rl_used == 0xffff makes the loop above walk far past the end of the block, dereferencing rl_recs[i] for i up to 65534. The resulting index is then handed to the sibling ocfs2_insert_refcount_rec(), whose insert-shift does: if (index < le16_to_cpu(rf_list->rl_used)) memmove(&rf_list->rl_recs[index + 1], &rf_list->rl_recs[index], (le16_to_cpu(rf_list->rl_used) - index) * sizeof(struct ocfs2_refcount_rec)); i.e. a memmove() of up to (0xffff - index) * 16 bytes (~1 MiB) from an offset already past the block. This is reachable from an ordinary reflink (FICLONE) against a crafted/corrupted ocfs2 image: attaching an extent whose cpos sorts past every real record in the leaf forces the lookup to run off the end instead of returning early on a match. The attacker model is local: CAP_SYS_ADMIN mounting a crafted or corrupted ocfs2 image, or a raw write to the block device backing an already-mounted ocfs2 filesystem. ocfs2_validate_refcount_block() already validates the block's ECC, signature, rf_blkno and rf_fs_generation, but never rl_count/rl_used against the block's actual on-disk capacity. This is the same class of gap that ocfs2_validate_extent_block() (fs/ocfs2/alloc.c) already closes for the sibling extent-list header, which checks both the record capacity and the "used" bound before any code walks h_list.l_recs[]: if (le16_to_cpu(eb->h_list.l_count) != ocfs2_extent_recs_per_eb(sb)) { rc = ocfs2_error(...); goto bail; } if (le16_to_cpu(eb->h_list.l_next_free_rec) > le16_to_cpu(eb->h_list.l_count)) { rc = ocfs2_error(...); goto bail; } Add the equivalent pair of checks to ocfs2_validate_refcount_block(): reject a refcount block whose rl_count does not match the fixed per-block capacity returned by ocfs2_refcount_recs_per_rb(), and reject rl_used > rl_count. Both checks are skipped when OCFS2_REFCOUNT_TREE_FL is set, because in that case the same union bytes hold an ocfs2_extent_list (rf_list), not the refcount record list (rf_records) -- that layout is already validated separately by ocfs2_validate_extent_block() when the referenced extent block is read. This mirrors the existing "!(rb->rf_flags & OCFS2_REFCOUNT_TREE_FL)" guard used elsewhere in this file (e.g. ocfs2_get_refcount_rec()) to decide whether rf_records or rf_list is the live member of the union. With this in place, a forged rl_used/rl_count is caught at block validation time (ocfs2_error()), consistent with every other corruption check in this function, instead of driving an out-of-bounds read in ocfs2_find_refcount_rec_in_rl() and a subsequent out-of-bounds memmove() in ocfs2_insert_refcount_rec(). Verified against a crafted image on a v6.19 KASAN (KASAN_GENERIC) build: replaying the same reflink (FICLONE) reliably hit a KASAN report in __ocfs2_increase_refcount()/ocfs2_insert_refcount_rec() before this patch, and triggers no report once ocfs2_validate_refcount_block() rejects the forged rl_used/rl_count. Link: https://lore.kernel.org/20260709132609.44233-1-security@auditcode.ai Fixes: f2c870e3b12e ("ocfs2: Add ocfs2_read_refcount_block.") Signed-off-by: Ibrahim Hashimov Reviewed-by: Joseph Qi Cc: Mark Fasheh Cc: Joel Becker Cc: Junxiao Bi Cc: Changwei Ge Cc: Jun Piao Cc: Heming Zhao Assisted-by: AuditCode-AI:2026.07 Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- fs/ocfs2/refcounttree.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) --- a/fs/ocfs2/refcounttree.c +++ b/fs/ocfs2/refcounttree.c @@ -116,6 +116,33 @@ static int ocfs2_validate_refcount_block le32_to_cpu(rb->rf_fs_generation)); goto out; } + + /* + * rf_records (rl_count/rl_used/rl_recs[]) is only meaningful when + * this block is not an interior tree block (OCFS2_REFCOUNT_TREE_FL); + * in that case the same union bytes hold an extent list (rf_list) + * instead, which is validated by ocfs2_validate_extent_block(). + */ + if (!(le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL)) { + if (le16_to_cpu(rb->rf_records.rl_count) != + ocfs2_refcount_recs_per_rb(sb)) { + rc = ocfs2_error(sb, + "Refcount block #%llu has an invalid rl_count of %u\n", + (unsigned long long)bh->b_blocknr, + le16_to_cpu(rb->rf_records.rl_count)); + goto out; + } + + if (le16_to_cpu(rb->rf_records.rl_used) > + le16_to_cpu(rb->rf_records.rl_count)) { + rc = ocfs2_error(sb, + "Refcount block #%llu has an invalid rl_used of %u (rl_count %u)\n", + (unsigned long long)bh->b_blocknr, + le16_to_cpu(rb->rf_records.rl_used), + le16_to_cpu(rb->rf_records.rl_count)); + goto out; + } + } out: return rc; }