From: Jiri Kosina Date: Thu, 14 Apr 2011 22:22:09 +0000 (-0700) Subject: brk: COMPAT_BRK: fix detection of randomized brk X-Git-Tag: v2.6.39-rc4~38 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=4471a675dfc7ca676c165079e91c712b09dc9ce4 brk: COMPAT_BRK: fix detection of randomized brk 5520e89 ("brk: fix min_brk lower bound computation for COMPAT_BRK") tried to get the whole logic of brk randomization for legacy (libc5-based) applications finally right. It turns out that the way to detect whether brk has actually been randomized in the end or not introduced by that patch still doesn't work for those binaries, as reported by Geert: : /sbin/init from my old m68k ramdisk exists prematurely. : : Before the patch: : : | brk(0x80005c8e) = 0x80006000 : : After the patch: : : | brk(0x80005c8e) = 0x80005c8e : : Old libc5 considers brk() to have failed if the return value is not : identical to the requested value. I don't like it, but currently see no better option than a bit flag in task_struct to catch the CONFIG_COMPAT_BRK && randomize_va_space == 2 case. Signed-off-by: Jiri Kosina Tested-by: Geert Uytterhoeven Reported-by: Geert Uytterhoeven Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index f34078d702d3..303983fabfd6 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -941,9 +941,13 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs) current->mm->start_stack = bprm->p; #ifdef arch_randomize_brk - if ((current->flags & PF_RANDOMIZE) && (randomize_va_space > 1)) + if ((current->flags & PF_RANDOMIZE) && (randomize_va_space > 1)) { current->mm->brk = current->mm->start_brk = arch_randomize_brk(current->mm); +#ifdef CONFIG_COMPAT_BRK + current->brk_randomized = 1; +#endif + } #endif if (current->personality & MMAP_PAGE_ZERO) { diff --git a/include/linux/sched.h b/include/linux/sched.h index 4ec2c027e92c..18d63cea2848 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1254,6 +1254,9 @@ struct task_struct { #endif struct mm_struct *mm, *active_mm; +#ifdef CONFIG_COMPAT_BRK + unsigned brk_randomized:1; +#endif #if defined(SPLIT_RSS_COUNTING) struct task_rss_stat rss_stat; #endif diff --git a/mm/mmap.c b/mm/mmap.c index 8c05e5b43b69..e27e0cf0de03 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -259,7 +259,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) * randomize_va_space to 2, which will still cause mm->start_brk * to be arbitrarily shifted */ - if (mm->start_brk > PAGE_ALIGN(mm->end_data)) + if (current->brk_randomized) min_brk = mm->start_brk; else min_brk = mm->end_data;