ensure ENOMEM is preserved in errno when appropriate

rcu_read_unlock may clobber errno, so it's our responsibility
to preserve it.  Fortunately, ENOMEM is the only error which
real_malloc can fail with.

Also, do not set errno for posix_memalign.

1 files changed, 15 insertions, 6 deletions

diff --git a/ext/mwrap/mwrap.c b/ext/mwrap/mwrap.c
index fa52631..7ae892c 100644
--- a/ext/mwrap/mwrap.c
+++ b/ext/mwrap/mwrap.c
@@ -401,10 +401,9 @@ static void *internal_memalign(size_t alignment, size_t size, uintptr_t caller)
         for (; alignment < sizeof(struct alloc_hdr); alignment *= 2)
                 ; /* double alignment until >= sizeof(struct alloc_hdr) */
         if (__builtin_add_overflow(size, alignment, &asize) ||
-            __builtin_add_overflow(asize, sizeof(struct alloc_hdr), &asize)) {
-                errno = ENOMEM;
+            __builtin_add_overflow(asize, sizeof(struct alloc_hdr), &asize))
                 return 0;
-        }
+
         /* assert(asize == (alignment + size + sizeof(struct alloc_hdr))); */
         rcu_read_lock();
         l = update_stats_rcu(size, caller);
@@ -423,7 +422,9 @@ static void *internal_memalign(size_t alignment, size_t size, uintptr_t caller)
 
 void *memalign(size_t alignment, size_t size)
 {
-        return internal_memalign(alignment, size, RETURN_ADDRESS(0));
+        void *p = internal_memalign(alignment, size, RETURN_ADDRESS(0));
+        if (caa_unlikely(!p)) errno = ENOMEM;
+        return p;
 }
 
 static bool is_power_of_two(size_t n) { return (n & (n - 1)) == 0; }
@@ -445,7 +446,9 @@ void cfree(void *) __attribute__((alias("free")));
 
 void *valloc(size_t size)
 {
-        return internal_memalign(page_size, size, RETURN_ADDRESS(0));
+        void *p = internal_memalign(page_size, size, RETURN_ADDRESS(0));
+        if (caa_unlikely(!p)) errno = ENOMEM;
+        return p;
 }
 
 #if __GNUC__ < 7
@@ -461,13 +464,16 @@ void *valloc(size_t size)
 void *pvalloc(size_t size)
 {
         size_t alignment = page_size;
+        void *p;
 
         if (add_overflow_p(size, alignment)) {
                 errno = ENOMEM;
                 return 0;
         }
         size = size_align(size, alignment);
-        return internal_memalign(alignment, size, RETURN_ADDRESS(0));
+        p = internal_memalign(alignment, size, RETURN_ADDRESS(0));
+        if (caa_unlikely(!p)) errno = ENOMEM;
+        return p;
 }
 
 void *malloc(size_t size)
@@ -490,6 +496,7 @@ void *malloc(size_t size)
                 p = hdr2ptr(h);
         }
         rcu_read_unlock();
+        if (caa_unlikely(!p)) errno = ENOMEM;
         return p;
 }
 
@@ -518,6 +525,7 @@ void *calloc(size_t nmemb, size_t size)
                 memset(p, 0, size);
         }
         rcu_read_unlock();
+        if (caa_unlikely(!p)) errno = ENOMEM;
         return p;
 }
 
@@ -552,6 +560,7 @@ void *realloc(void *ptr, size_t size)
                 memcpy(p, ptr, old->size < size ? old->size : size);
                 free(ptr);
         }
+        if (caa_unlikely(!p)) errno = ENOMEM;
         return p;
 }