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exec: fix stack excutability without PT_GNU_STACK

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Kernel Bugzilla #11063 points out that on some architectures (e.g. x86_32)
exec'ing an ELF without a PT_GNU_STACK program header should default to an
executable stack; but this got broken by the unlimited argv feature because
stack vma is now created before the right personality has been established:
so breaking old binaries using nested function trampolines.

Therefore re-evaluate VM_STACK_FLAGS in setup_arg_pages, where stack
vm_flags used to be set, before the mprotect_fixup.  Checking through
our existing VM_flags, none would have changed since insert_vm_struct:
so this seems safer than finding a way through the personality labyrinth.

Reported-by: pageexec@freemail.hu
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2008-07-10 21:19:20 +01:00 committed by Linus Torvalds
parent f8804d3946
commit 96a8e13ed4
1 changed files with 1 additions and 1 deletions
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2
fs/exec.c
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@ -610,7 +610,7 @@ int setup_arg_pages(struct linux_binprm *bprm,
bprm->exec -= stack_shift;
down_write(&mm->mmap_sem);
vm_flags = vma->vm_flags;
vm_flags = VM_STACK_FLAGS;
/*
* Adjust stack execute permissions; explicitly enable for