linux-kernel - [patch alternative] mm, page_alloc: warn for non-blockable __GFP

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 for Android: free password hash cracker in your pocket

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

Message-ID: <alpine.DEB.2.02.1312101618530.22701@chino.kir.corp.google.com>
Date:	Tue, 10 Dec 2013 16:19:21 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...e.cz>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [patch alternative] mm, page_alloc: warn for non-blockable __GFP_NOFAIL
 allocation failure

__GFP_NOFAIL may return NULL when coupled with GFP_NOWAIT or GFP_ATOMIC.

Luckily, nothing currently does such craziness.  So instead of causing
such allocations to loop (potentially forever), we maintain the current
behavior and also warn about the new users of the deprecated flag.

Suggested-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 mm/page_alloc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2536,8 +2536,15 @@ rebalance:
 	}
 
 	/* Atomic allocations - we can't balance anything */
-	if (!wait)
+	if (!wait) {
+		/*
+		 * All existing users of the deprecated __GFP_NOFAIL are
+		 * blockable, so warn of any new users that actually allow this
+		 * type of allocation to fail.
+		 */
+		WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL);
 		goto nopage;
+	}
 
 	/* Avoid recursion of direct reclaim */
 	if (current->flags & PF_MEMALLOC)
--
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/