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authorLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-03 10:12:14 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-03 10:12:14 -0800
commita64e715fc74b1a7dcc5944f848acc38b2c4d4ee2 (patch)
tree6a5dfc2b0ff946406082a8ad4dc046964d259dea
parenta345b4ba2086bacc63884e5d72268415a97bcbff (diff)
Allow ARG_MAX execve string space even with a small stack limit
The new code that removed the limitation on the execve string size (which was historically 32 pages) replaced it with a much softer limit based on RLIMIT_STACK which is usually much larger than the traditional limit. See commit b6a2fea39318e43fee84fa7b0b90d68bed92d2ba ("mm: variable length argument support") for details. However, if you have a small stack limit (perhaps because you need lots of stacks in a threaded environment), the new heuristic of allowing up to 1/4th of RLIMIT_STACK to be used for argument and environment strings could actually be smaller than the old limit. So just say that it's ok to have up to ARG_MAX strings regardless of the value of RLIMIT_STACK, and check the rlimit only when going over that traditional limit. (Of course, if you actually have a *really* small stack limit, the whole stack itself will be limited before you hit ARG_MAX, but that has always been true and is clearly the right behaviour anyway). Acked-by: Carlos O'Donell <carlos@codesourcery.com> Cc: Michael Kerrisk <michael.kerrisk@googlemail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ollie Wild <aaw@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/exec.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/fs/exec.c b/fs/exec.c
index a44b142fb46..54a0a557b67 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -173,8 +173,15 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
return NULL;
if (write) {
- struct rlimit *rlim = current->signal->rlim;
unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
+ struct rlimit *rlim;
+
+ /*
+ * We've historically supported up to 32 pages (ARG_MAX)
+ * of argument strings even with small stacks
+ */
+ if (size <= ARG_MAX)
+ return page;
/*
* Limit to 1/4-th the stack size for the argv+env strings.
@@ -183,6 +190,7 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
* - the program will have a reasonable amount of stack left
* to work from.
*/
+ rlim = current->signal->rlim;
if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
put_page(page);
return NULL;