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Fix a potential NULL pointer dereference in _init_thread().

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The first NULL pointer check against `attr' suggests that `attr' can
be NULL.  Then later `attr' is directly dereferenced, suggesting the
opposite.

    if (attr == NULL) {
        ...
    } else {
        ...
    }
    ...
    if (attr->stack_base == ...) { ... }

The public API pthread_create(3) allows NULL, and interprets it as "default".
Our implementation actually swaps in a pointer to the global default
pthread_attr_t, so we don't need any NULL checks in _init_thread. (The other
internal caller passes its own pthread_attr_t.)

Change-Id: I0a4e79b83f5989249556a07eed1f2887e96c915e
Signed-off-by: Xi Wang <xi.wang@gmail.com>
This commit is contained in:
Xi Wang 2012-10-27 02:02:01 -04:00 committed by Elliott Hughes
parent 33c4a3adde
commit ae8eb74675
2 changed files with 7 additions and 10 deletions
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15
libc/bionic/pthread.c
View File

@ -211,18 +211,14 @@ void __thread_entry(int (*func)(void*), void *arg, void **tls)
#include <private/logd.h>
__LIBC_ABI_PRIVATE__
int _init_thread(pthread_internal_t* thread, pid_t kernel_id, pthread_attr_t* attr,
int _init_thread(pthread_internal_t* thread, pid_t kernel_id, const pthread_attr_t* attr,
void* stack_base, bool add_to_thread_list)
{
int error = 0;
if (attr == NULL) {
thread->attr = gDefaultPthreadAttr;
} else {
thread->attr = *attr;
}
thread->attr = *attr;
thread->attr.stack_base = stack_base;
thread->kernel_id = kernel_id;
thread->kernel_id = kernel_id;
// Make a note of whether the user supplied this stack (so we know whether or not to free it).
if (attr->stack_base == stack_base) {
@ -234,7 +230,8 @@ int _init_thread(pthread_internal_t* thread, pid_t kernel_id, pthread_attr_t* at
struct sched_param param;
param.sched_priority = thread->attr.sched_priority;
if (sched_setscheduler(kernel_id, thread->attr.sched_policy, &param) == -1) {
// For back compat reasons, we just warn about possible invalid sched_policy
// For backwards compatibility reasons, we just warn about failures here.
// error = errno;
const char* msg = "pthread_create sched_setscheduler call failed: %s\n";
__libc_android_log_print(ANDROID_LOG_WARN, "libc", msg, strerror(errno));
}
@ -361,7 +358,7 @@ int pthread_create(pthread_t *thread_out, pthread_attr_t const * attr,
return clone_errno;
}
int init_errno = _init_thread(thread, tid, (pthread_attr_t*) attr, stack, true);
int init_errno = _init_thread(thread, tid, attr, stack, true);
if (init_errno != 0) {
// Mark the thread detached and let its __thread_entry run to
// completion. (It'll just exit immediately, cleaning up its resources.)

2
libc/bionic/pthread_internal.h
View File

@ -54,7 +54,7 @@ typedef struct pthread_internal_t
char dlerror_buffer[__BIONIC_DLERROR_BUFFER_SIZE];
} pthread_internal_t;
int _init_thread(pthread_internal_t* thread, pid_t kernel_id, pthread_attr_t* attr,
int _init_thread(pthread_internal_t* thread, pid_t kernel_id, const pthread_attr_t* attr,
void* stack_base, bool add_to_thread_list);
void _pthread_internal_add( pthread_internal_t* thread );
pthread_internal_t* __get_thread(void);