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[PATCH v2][BZ #22637] Fix stack guard size accounting
- From: Szabolcs Nagy <szabolcs dot nagy at arm dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Cc: nd at arm dot com, Carlos O'Donell <carlos at redhat dot com>, Florian Weimer <fweimer at redhat dot com>
- Date: Mon, 08 Jan 2018 18:04:42 +0000
- Subject: [PATCH v2][BZ #22637] Fix stack guard size accounting
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v2:
- use separate bug number from the tls accounting issue.
- check for arithmetic overflows.
Previously if user requested S stack and G guard when creating a
thread, the total mapping was S and the actual available stack was
S - G - static_tls, which is not what the user requested.
This patch fixes the guard size accounting by pretending the user
requested S+G stack. This way all later logic works out except
when reporting the user requested stack size (pthread_getattr_np)
or when computing the minimal stack size (__pthread_get_minstack).
Normally this will increase thread stack allocations by one page.
TLS accounting is not affected, that will require a separate fix.
[BZ #22637]
* nptl/allocatestack.c (allocate_stack): Add guardsize to stacksize.
* nptl/nptl-init.c (__pthread_get_minstack): Remove guardsize from
stacksize.
* nptl/pthread_getattr_np.c (pthread_getattr_np): Likewise.
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 05b8ed331b..b374f4794d 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -532,6 +532,10 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
/* Make sure the size of the stack is enough for the guard and
eventually the thread descriptor. */
guardsize = (attr->guardsize + pagesize_m1) & ~pagesize_m1;
+ if (guardsize < attr->guardsize || size + guardsize < guardsize)
+ /* Arithmetic overflow. */
+ return EINVAL;
+ size += guardsize;
if (__builtin_expect (size < ((guardsize + __static_tls_size
+ MINIMAL_REST_STACK + pagesize_m1)
& ~pagesize_m1),
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index c237a3675a..5a4b52419f 100644
--- a/nptl/nptl-init.c
+++ b/nptl/nptl-init.c
@@ -472,8 +472,5 @@ strong_alias (__pthread_initialize_minimal_internal,
size_t
__pthread_get_minstack (const pthread_attr_t *attr)
{
- struct pthread_attr *iattr = (struct pthread_attr *) attr;
-
- return (GLRO(dl_pagesize) + __static_tls_size + PTHREAD_STACK_MIN
- + iattr->guardsize);
+ return GLRO(dl_pagesize) + __static_tls_size + PTHREAD_STACK_MIN;
}
diff --git a/nptl/pthread_getattr_np.c b/nptl/pthread_getattr_np.c
index 961d711fd2..c79fd7b4ec 100644
--- a/nptl/pthread_getattr_np.c
+++ b/nptl/pthread_getattr_np.c
@@ -57,9 +57,10 @@ pthread_getattr_np (pthread_t thread_id, pthread_attr_t *attr)
/* The sizes are subject to alignment. */
if (__glibc_likely (thread->stackblock != NULL))
{
- iattr->stacksize = thread->stackblock_size;
+ iattr->stacksize = thread->stackblock_size - thread->guardsize;
#if _STACK_GROWS_DOWN
- iattr->stackaddr = (char *) thread->stackblock + iattr->stacksize;
+ iattr->stackaddr = (char *) thread->stackblock
+ + thread->stackblock_size;
#else
iattr->stackaddr = (char *) thread->stackblock;
#endif