This is the mail archive of the
mailing list for the glibc project.
Re: [PATCH][BZ #11787] Fix stack guard size accounting
- From: Florian Weimer <fweimer at redhat dot com>
- To: Szabolcs Nagy <szabolcs dot nagy at arm dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Cc: nd at arm dot com
- Date: Wed, 20 Dec 2017 14:09:29 +0100
- Subject: Re: [PATCH][BZ #11787] Fix stack guard size accounting
- Authentication-results: sourceware.org; auth=none
- References: <5A2FE5ED.firstname.lastname@example.org>
On 12/12/2017 03:21 PM, Szabolcs Nagy wrote:
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.
Should this fix use a separate bug number?
2017-12-12 Szabolcs Nagy<email@example.com>
* nptl/allocatestack.c (allocate_stack): Add guardsize to stacksize.
* nptl/nptl-init.c (__pthread_get_minstack): Remove guardsize from
* nptl/pthread_getattr_np.c (pthread_getattr_np): Likewise.
Patch looks good in general. The computation for stackblock_size looks
right to me.
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 1cc789319564b468cf07bdb1304b27dc5a91e86f..9525322b1f92bb34aa21dcab28566aecd7434e90 100644
@@ -532,6 +532,7 @@ 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;
+ size += guardsize;
if (__builtin_expect (size < ((guardsize + __static_tls_size
+ MINIMAL_REST_STACK + pagesize_m1)
I wonder if we should add an overflow check there and return EINVAL if
guardsize < attr->guardsize || size + guardsize < guardsize