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Commit 4ac31311 authored by Rich Felker's avatar Rich Felker Committed by Greg Ungerer
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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: default avatarRich Felker <dalias@libc.org>
Acked-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarGreg Ungerer <gerg@uclinux.org>
parent 32b88194

fs/binfmt_elf_fdpic.c

+1 −6
Original line number Original line Diff line number Diff line
@@ -374,10 +374,7 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) 
		PAGE_ALIGN(current->mm->start_brk);

		PAGE_ALIGN(current->mm->start_brk);





#else

#else

	/* create a stack and brk area big enough for everyone

	/* create a stack area and zero-size brk area */

	 * - the brk heap starts at the bottom and works up

	 * - the stack starts at the top and works down

	 */

	stack_size = (stack_size + PAGE_SIZE - 1) & PAGE_MASK;

	stack_size = (stack_size + PAGE_SIZE - 1) & PAGE_MASK;

	if (stack_size < PAGE_SIZE * 2)

	if (stack_size < PAGE_SIZE * 2)

		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->brk = current->mm->start_brk;

	current->mm->context.end_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;

	current->mm->start_stack = current->mm->start_brk + stack_size;

#endif

#endif