path: root/fs
diff options
authorJiri Kosina <jkosina@suse.cz>2008-01-30 13:30:40 +0100
committerIngo Molnar <mingo@elte.hu>2008-01-30 13:30:40 +0100
commitc1d171a002942ea2d93b4fbd0c9583c56fce0772 (patch)
tree49249c927dc1644e7c92150808269cb474bdd411 /fs
parent7b83dae7aa31db4f6d6e78c3c6d490a7ac58699c (diff)
x86: randomize brk
Randomize the location of the heap (brk) for i386 and x86_64. The range is randomized in the range starting at current brk location up to 0x02000000 offset for both architectures. This, together with pie-executable-randomization.patch and pie-executable-randomization-fix.patch, should make the address space randomization on i386 and x86_64 complete. Arjan says: This is known to break older versions of some emacs variants, whose dumper code assumed that the last variable declared in the program is equal to the start of the dynamically allocated memory region. (The dumper is the code where emacs effectively dumps core at the end of it's compilation stage; this coredump is then loaded as the main program during normal use) iirc this was 5 years or so; we found this way back when I was at RH and we first did the security stuff there (including this brk randomization). It wasn't all variants of emacs, and it got fixed as a result (I vaguely remember that emacs already had code to deal with it for other archs/oses, just ifdeffed wrongly). It's a rare and wrong assumption as a general thing, just on x86 it mostly happened to be true (but to be honest, it'll break too if gcc does something fancy or if the linker does a non-standard order). Still its something we should at least document. Note 2: afaik it only broke the emacs *build*. I'm not 100% sure about that (it IS 5 years ago) though. [ akpm@linux-foundation.org: deuglification ] Signed-off-by: Jiri Kosina <jkosina@suse.cz> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Roland McGrath <roland@redhat.com> Cc: Jakub Jelinek <jakub@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'fs')
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index f0b3171842f..043a800c8f7 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1021,6 +1021,12 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
current->mm->end_data = end_data;
current->mm->start_stack = bprm->p;
+#ifdef arch_randomize_brk
+ if (current->flags & PF_RANDOMIZE)
+ current->mm->brk = current->mm->start_brk =
+ arch_randomize_brk(current->mm);
if (current->personality & MMAP_PAGE_ZERO) {
/* Why this, you ask??? Well SVr4 maps page 0 as read-only,
and some applications "depend" upon this behavior.