linux-kernel - [ 77/95] fs/buffer.c: remove BUG() in possible but rare condition

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]

Date:	Sun, 09 Sep 2012 23:43:07 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Glauber Costa <glommer@...allels.com>,
	Michal Hocko <mhocko@...e.cz>
Subject: [ 77/95] fs/buffer.c: remove BUG() in possible but rare condition

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Glauber Costa <glommer@...allels.com>

commit 61065a30af8df4b8989c2ac7a1f4b4034e4df2d5 upstream.

While stressing the kernel with with failing allocations today, I hit the
following chain of events:

alloc_page_buffers():

	bh = alloc_buffer_head(GFP_NOFS);
	if (!bh)
		goto no_grow; <= path taken

grow_dev_page():
        bh = alloc_page_buffers(page, size, 0);
        if (!bh)
                goto failed;  <= taken, consequence of the above

and then the failed path BUG()s the kernel.

The failure is inserted a litte bit artificially, but even then, I see no
reason why it should be deemed impossible in a real box.

Even though this is not a condition that we expect to see around every
time, failed allocations are expected to be handled, and BUG() sounds just
too much.  As a matter of fact, grow_dev_page() can return NULL just fine
in other circumstances, so I propose we just remove it, then.

Signed-off-by: Glauber Costa <glommer@...allels.com>
Cc: Michal Hocko <mhocko@...e.cz>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/buffer.c |    1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 36d6665..351e18e 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -985,7 +985,6 @@ grow_dev_page(struct block_device *bdev, sector_t block,
 	return page;
 
 failed:
-	BUG();
 	unlock_page(page);
 	page_cache_release(page);
 	return NULL;


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/