From 5d4c589ca4b527f24f04b8ad23c579499aa510bc Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Mon, 15 Jan 2018 16:06:31 +0100 Subject: [PATCH] [BZ #22637] Fix stack guard size accounting 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/descr.h (stackblock, stackblock_size): Update comments. * 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. (cherry picked from commit 630f4cc3aa019ede55976ea561f1a7af2f068639) --- ChangeLog | 9 +++++++++ NEWS | 1 + nptl/allocatestack.c | 4 ++++ nptl/descr.h | 4 ++-- nptl/nptl-init.c | 5 +---- nptl/pthread_getattr_np.c | 7 +++++-- 6 files changed, 22 insertions(+), 8 deletions(-) diff --git a/ChangeLog b/ChangeLog index 17dd1a2a52..0e80c8e4c6 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,12 @@ +2018-01-08 Szabolcs Nagy + + [BZ #22637] + * nptl/descr.h (stackblock, stackblock_size): Update comments. + * 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. + 2018-01-08 Florian Weimer * nptl/tst-thread-exit-clobber.cc: New file. diff --git a/NEWS b/NEWS index 1cad04eb0e..fb54fa069c 100644 --- a/NEWS +++ b/NEWS @@ -67,6 +67,7 @@ The following bugs are resolved with this release: [22078] nss_files performance issue in hosts multi mode [22322] libc: [mips64] wrong bits/long-double.h installed [22627] $ORIGIN in $LD_LIBRARY_PATH is substituted twice + [22637] nptl: Fix stack guard size accounting [22679] getcwd(3) can succeed without returning an absolute path (CVE-2018-1000001) diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c index 368fe3c36b..a1d1be5dfb 100644 --- a/nptl/allocatestack.c +++ b/nptl/allocatestack.c @@ -482,6 +482,10 @@ 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/descr.h b/nptl/descr.h index a145860f07..b63204a992 100644 --- a/nptl/descr.h +++ b/nptl/descr.h @@ -382,9 +382,9 @@ struct pthread /* Machine-specific unwind info. */ struct _Unwind_Exception exc; - /* If nonzero pointer to area allocated for the stack and its - size. */ + /* If nonzero, pointer to the area allocated for the stack and guard. */ void *stackblock; + /* Size of the stackblock area including the guard. */ size_t stackblock_size; /* Size of the included guard area. */ size_t guardsize; diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c index 2f8599b391..1ca783e466 100644 --- a/nptl/nptl-init.c +++ b/nptl/nptl-init.c @@ -473,8 +473,5 @@ 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 06093b3d92..210a3f8a1f 100644 --- a/nptl/pthread_getattr_np.c +++ b/nptl/pthread_getattr_np.c @@ -57,9 +57,12 @@ 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; + /* The stack size reported to the user should not include the + guard 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