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[v2,1/2] malloc: Fix a realloc crash with heap tagging [BZ 27468]

Message ID a8e37914688a733e2b49820e6fc6ef9160378b99.1615483341.git.szabolcs.nagy@arm.com
State Committed
Delegated to: DJ Delorie
Headers show
Series malloc: split the mtag realloc fix patch | expand

Commit Message

Szabolcs Nagy March 11, 2021, 5:57 p.m. UTC
_int_free must be called with a chunk that has its tag reset. This was
missing in a rare case that could crash when heap tagging is enabled:
when in a multi-threaded process the current arena runs out of memory
during realloc, but another arena still has space to finish the realloc
then _int_free was called without clearing the user allocation tags.

Fixes bug 27468.

Reviewed-by: DJ Delorie <dj@redhat.com>
 malloc/malloc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
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diff --git a/malloc/malloc.c b/malloc/malloc.c
index 1f4bbd8edf..8f8f12c276 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3446,7 +3446,9 @@  __libc_realloc (void *oldmem, size_t bytes)
       newp = __libc_malloc (bytes);
       if (newp != NULL)
-          memcpy (newp, oldmem, oldsize - SIZE_SZ);
+	  size_t sz = CHUNK_AVAILABLE_SIZE (oldp) - CHUNK_HDR_SZ;
+	  memcpy (newp, oldmem, sz);
+	  (void) TAG_REGION (chunk2rawmem (oldp), sz);
           _int_free (ar_ptr, oldp, 0);