The patch titled fs/exec.c: restrict initial stack space expansion to rlimit has been removed from the -mm tree. Its filename was fs-execc-restrict-initial-stack-space-expansion-to-rlimit.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: fs/exec.c: restrict initial stack space expansion to rlimit From: Michael Neuling <mikey@xxxxxxxxxxx> When reserving stack space for a new process, make sure we're not attempting to expand the stack by more than rlimit allows. This fixes a bug caused by b6a2fea39318e43fee84fa7b0b90d68bed92d2ba ("mm: variable length argument support") and unmasked by fc63cf237078c86214abcb2ee9926d8ad289da9b ("exec: setup_arg_pages() fails to return errors"). This bug means that when limiting the stack to less the 20*PAGE_SIZE (eg. 80K on 4K pages or 'ulimit -s 79') all processes will be killed before they start. This is particularly bad with 64K pages, where a ulimit below 1280K will kill every process. To test, do: 'ulimit -s 15; ls' before and after the patch is applied. Before it's applied, 'ls' should be killed. After the patch is applied, 'ls' should no longer be killed. A stack limit of 15KB since it's small enough to trigger 20*PAGE_SIZE. Also 15KB not a multiple of PAGE_SIZE, which is a trickier case to handle correctly with this code. 4K pages should be fine to test with. [kosaki.motohiro@xxxxxxxxxxxxxx: cleanup] [akpm@xxxxxxxxxxxxxxxxxxxx: cleanup cleanup] Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Cc: Americo Wang <xiyou.wangcong@xxxxxxxxx> Cc: Anton Blanchard <anton@xxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: James Morris <jmorris@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Serge Hallyn <serue@xxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/exec.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff -puN fs/exec.c~fs-execc-restrict-initial-stack-space-expansion-to-rlimit fs/exec.c --- a/fs/exec.c~fs-execc-restrict-initial-stack-space-expansion-to-rlimit +++ a/fs/exec.c @@ -571,6 +571,9 @@ int setup_arg_pages(struct linux_binprm struct vm_area_struct *prev = NULL; unsigned long vm_flags; unsigned long stack_base; + unsigned long stack_size; + unsigned long stack_expand; + unsigned long rlim_stack; #ifdef CONFIG_STACK_GROWSUP /* Limit stack size to 1GB */ @@ -627,10 +630,24 @@ int setup_arg_pages(struct linux_binprm goto out_unlock; } + stack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE; + stack_size = vma->vm_end - vma->vm_start; + /* + * Align this down to a page boundary as expand_stack + * will align it up. + */ + rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; + rlim_stack = min(rlim_stack, stack_size); #ifdef CONFIG_STACK_GROWSUP - stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE; + if (stack_size + stack_expand > rlim_stack) + stack_base = vma->vm_start + rlim_stack; + else + stack_base = vma->vm_end + stack_expand; #else - stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE; + if (stack_size + stack_expand > rlim_stack) + stack_base = vma->vm_end - rlim_stack; + else + stack_base = vma->vm_start - stack_expand; #endif ret = expand_stack(vma, stack_base); if (ret) _ Patches currently in -mm which might be from mikey@xxxxxxxxxxx are origin.patch linux-next.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html