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defer free of thread-local dlerror buffers from inconsistent context

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__dl_thread_cleanup is called from the context of an exiting thread
that is not in a consistent state valid for calling application code.
since commit c9f415d7ea, it's possible
(and supported usage) for the allocator to have been replaced by the
application, so __dl_thread_cleanup can no longer call free. instead,
reuse the message buffer as a linked-list pointer, and queue it to be
freed the next time any dynamic linker error message is generated.
This commit is contained in:
Rich Felker 2019-02-15 14:20:49 -05:00
parent b2020571f0
commit aa5a9d15e0
1 changed files with 20 additions and 2 deletions
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22
src/ldso/dlerror.c
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@ -3,6 +3,7 @@
#include <stdarg.h> #include <stdarg.h>
#include "pthread_impl.h" #include "pthread_impl.h"
#include "dynlink.h" #include "dynlink.h"
#include "lock.h"
char *dlerror() char *dlerror()
{ {
@ -16,21 +17,38 @@ char *dlerror()
return s; return s;
} }
static volatile int freebuf_queue_lock[1];
static void **freebuf_queue;
void __dl_thread_cleanup(void) void __dl_thread_cleanup(void)
{ {
pthread_t self = __pthread_self(); pthread_t self = __pthread_self();
if (self->dlerror_buf != (void *)-1) if (self->dlerror_buf && self->dlerror_buf != (void *)-1) {
free(self->dlerror_buf); LOCK(freebuf_queue_lock);
void **p = (void **)self->dlerror_buf;
*p = freebuf_queue;
freebuf_queue = p;
UNLOCK(freebuf_queue_lock);
}
} }
hidden void __dl_vseterr(const char *fmt, va_list ap) hidden void __dl_vseterr(const char *fmt, va_list ap)
{ {
LOCK(freebuf_queue_lock);
while (freebuf_queue) {
void **p = freebuf_queue;
freebuf_queue = *p;
free(p);
}
UNLOCK(freebuf_queue_lock);
va_list ap2; va_list ap2;
va_copy(ap2, ap); va_copy(ap2, ap);
pthread_t self = __pthread_self(); pthread_t self = __pthread_self();
if (self->dlerror_buf != (void *)-1) if (self->dlerror_buf != (void *)-1)
free(self->dlerror_buf); free(self->dlerror_buf);
size_t len = vsnprintf(0, 0, fmt, ap2); size_t len = vsnprintf(0, 0, fmt, ap2);
if (len < sizeof(void *)) len = sizeof(void *);
va_end(ap2); va_end(ap2);
char *buf = malloc(len+1); char *buf = malloc(len+1);
if (buf) { if (buf) {