linux-kernel - [149/262] binfmt_elf: fix PIE execution with randomization disabled

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Date:	Wed, 09 Nov 2011 13:27:51 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Jiri Kosina <jkosina@...e.cz>,
	Ingo Molnar <mingo@...e.hu>,
	Russell King <rmk@....linux.org.uk>,
	"H.J. Lu" <hongjiu.lu@...el.com>, <stable@...nel.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>
Subject: [149/262] binfmt_elf: fix PIE execution with randomization disabled

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

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

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

commit a3defbe5c337dbc6da911f8cc49ae3cc3b49b453 upstream.

The case of address space randomization being disabled in runtime through
randomize_va_space sysctl is not treated properly in load_elf_binary(),
resulting in SIGKILL coming at exec() time for certain PIE-linked binaries
in case the randomization has been disabled at runtime prior to calling
exec().

Handle the randomize_va_space == 0 case the same way as if we were not
supporting .text randomization at all.

Based on original patch by H.J. Lu and Josh Boyer.

Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Russell King <rmk@....linux.org.uk>
Cc: H.J. Lu <hongjiu.lu@...el.com>
Cc: <stable@...nel.org>
Tested-by: Josh Boyer <jwboyer@...hat.com>
Acked-by: Nicolas Pitre <nicolas.pitre@...aro.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/binfmt_elf.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -796,7 +796,16 @@ static int load_elf_binary(struct linux_
 			 * might try to exec.  This is because the brk will
 			 * follow the loader, and is not movable.  */
 #if defined(CONFIG_X86) || defined(CONFIG_ARM)
-			load_bias = 0;
+			/* Memory randomization might have been switched off
+			 * in runtime via sysctl.
+			 * If that is the case, retain the original non-zero
+			 * load_bias value in order to establish proper
+			 * non-randomized mappings.
+			 */
+			if (current->flags & PF_RANDOMIZE)
+				load_bias = 0;
+			else
+				load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
 #else
 			load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
 #endif

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