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authorAndi Kleen <ak@suse.de>2006-03-25 10:29:09 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-25 12:10:52 -0500
commit913bd906019514579b3c7ec5ab9c463e89207a57 (patch)
tree8f73c66bf2b30afb2807814d97f9307af0508454 /fs/binfmt_elf.c
parentdca99a38bccceda9e079d4c95abefbd9028605fe (diff)
[PATCH] x86_64: Increase the variability of the process stack on 64bit architectures
8MB is not really very random, use 1GB (or more with larger page sizes) instead. Also use the low bits of the random generator output now instead of throwing them away. Only enabled on x86-64 right now. Other architectures need to add a suitable STACK_RND_MASK Cc: mingo@elte.hu Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/binfmt_elf.c')
-rw-r--r--fs/binfmt_elf.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 4349113881fb..537893a16014 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -500,17 +500,22 @@ out:
500#define INTERPRETER_AOUT 1 500#define INTERPRETER_AOUT 1
501#define INTERPRETER_ELF 2 501#define INTERPRETER_ELF 2
502 502
503#ifndef STACK_RND_MASK
504#define STACK_RND_MASK 0x7ff /* with 4K pages 8MB of VA */
505#endif
503 506
504static unsigned long randomize_stack_top(unsigned long stack_top) 507static unsigned long randomize_stack_top(unsigned long stack_top)
505{ 508{
506 unsigned int random_variable = 0; 509 unsigned int random_variable = 0;
507 510
508 if (current->flags & PF_RANDOMIZE) 511 if (current->flags & PF_RANDOMIZE) {
509 random_variable = get_random_int() % (8*1024*1024); 512 random_variable = get_random_int() & STACK_RND_MASK;
513 random_variable <<= PAGE_SHIFT;
514 }
510#ifdef CONFIG_STACK_GROWSUP 515#ifdef CONFIG_STACK_GROWSUP
511 return PAGE_ALIGN(stack_top + random_variable); 516 return PAGE_ALIGN(stack_top) + random_variable;
512#else 517#else
513 return PAGE_ALIGN(stack_top - random_variable); 518 return PAGE_ALIGN(stack_top) - random_variable;
514#endif 519#endif
515} 520}
516 521