linux-kernel - [PATCH 5.13 032/800] gfs2: Fix underflow in gfs2_page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210712060917.749912640@linuxfoundation.org>
Date:   Mon, 12 Jul 2021 08:00:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Bob Peterson <rpeterso@...hat.com>,
        Andreas Gruenbacher <agruenba@...hat.com>
Subject: [PATCH 5.13 032/800] gfs2: Fix underflow in gfs2_page_mkwrite

From: Andreas Gruenbacher <agruenba@...hat.com>

commit d3c51c55cb9274dd43c156f1f26b5eb4d5f2d58c upstream.

On filesystems with a block size smaller than PAGE_SIZE and non-empty
files smaller then PAGE_SIZE, gfs2_page_mkwrite could end up allocating
excess blocks beyond the end of the file, similar to fallocate.  This
doesn't make sense; fix it.

Reported-by: Bob Peterson <rpeterso@...hat.com>
Fixes: 184b4e60853d ("gfs2: Fix end-of-file handling in gfs2_page_mkwrite")
Cc: stable@...r.kernel.org # v5.5+
Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/gfs2/file.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -450,8 +450,8 @@ static vm_fault_t gfs2_page_mkwrite(stru
 	file_update_time(vmf->vma->vm_file);
 
 	/* page is wholly or partially inside EOF */
-	if (offset > size - PAGE_SIZE)
-		length = offset_in_page(size);
+	if (size - offset < PAGE_SIZE)
+		length = size - offset;
 	else
 		length = PAGE_SIZE;