linux-kernel - [PATCH 1/2] brk: check the lower bound properly

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:	Wed, 6 Feb 2008 14:45:16 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...radead.org>,
	Hugh Dickins <hugh@...itas.com>, Pavel Machek <pavel@...e.cz>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] brk: check the lower bound properly

From: Jiri Kosina <jkosina@...e.cz>

brk: check the lower bound properly

There is a check in sys_brk(), that tries to make sure that we do not
underflow the area that is dedicated to brk heap.

The check is however wrong, as it assumes that brk area starts immediately
after the end of the code (+bss), which is wrong for example in
environments with randomized brk start. The proper way is to check whether
the address is not below the start_brk address.

Cc: Ingo Molnar <mingo@...e.hu>
Cc: Arjan van de Ven <arjan@...radead.org>
Acked-by: Hugh Dickins <hugh@...itas.com>
Acked-by: Pavel Machek <pavel@...e.cz>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>

diff --git a/mm/mmap.c b/mm/mmap.c
index 8295577..1c3b48f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -241,7 +241,7 @@ asmlinkage unsigned long sys_brk(unsigned long brk)
 
 	down_write(&mm->mmap_sem);
 
-	if (brk < mm->end_code)
+	if (brk < mm->start_brk)
 		goto out;
 
 	/*
--
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/