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fs/binfmt_elf_fdpic.c: fix brk area overlap with stack on NOMMU 

On NOMMU archs, the FDPIC ELF loader sets up the usable brk range to
overlap with all but the last PAGE_SIZE bytes of the stack. This leads
to catastrophic memory reuse/corruption if brk is used. Fix by setting
the brk area to zero size to disable its use.

Signed-off-by: Rich Felker <dalias@libc.org>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
This commit is contained in:
Rich Felker 2015-08-20 15:11:06 -04:00 committed by Greg Ungerer
parent 32b88194f7
commit 4ac3131110
1 changed files with 1 additions and 6 deletions
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7
fs/binfmt_elf_fdpic.c
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@ -374,10 +374,7 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm)
PAGE_ALIGN(current->mm->start_brk);
#else
/* create a stack and brk area big enough for everyone
* - the brk heap starts at the bottom and works up
* - the stack starts at the top and works down
*/
/* create a stack area and zero-size brk area */
stack_size = (stack_size + PAGE_SIZE - 1) & PAGE_MASK;
if (stack_size < PAGE_SIZE * 2)
stack_size = PAGE_SIZE * 2;
@ -400,8 +397,6 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm)
current->mm->brk = current->mm->start_brk;
current->mm->context.end_brk = current->mm->start_brk;
current->mm->context.end_brk +=
(stack_size > PAGE_SIZE) ? (stack_size - PAGE_SIZE) : 0;
current->mm->start_stack = current->mm->start_brk + stack_size;
#endif