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commit b50dd3bc8cbb1efe85399b03d7e6c0310c2ead84
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Author: Florian Weimer <fw@deneb.enyo.de>
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Date: Mon Dec 31 22:04:36 2018 +0100
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malloc: Always call memcpy in _int_realloc [BZ #24027]
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This commit removes the custom memcpy implementation from _int_realloc
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for small chunk sizes. The ncopies variable has the wrong type, and
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an integer wraparound could cause the existing code to copy too few
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elements (leaving the new memory region mostly uninitialized).
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Therefore, removing this code fixes bug 24027.
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diff --git a/malloc/malloc.c b/malloc/malloc.c
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index 7bfa66a56786d110..0234d968c0ce65a0 100644
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--- a/malloc/malloc.c
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+++ b/malloc/malloc.c
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@@ -4532,11 +4532,6 @@ _int_realloc(mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
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mchunkptr remainder; /* extra space at end of newp */
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unsigned long remainder_size; /* its size */
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- unsigned long copysize; /* bytes to copy */
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- unsigned int ncopies; /* INTERNAL_SIZE_T words to copy */
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- INTERNAL_SIZE_T* s; /* copy source */
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- INTERNAL_SIZE_T* d; /* copy destination */
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-
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/* oldmem size */
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if (__builtin_expect (chunksize_nomask (oldp) <= 2 * SIZE_SZ, 0)
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|| __builtin_expect (oldsize >= av->system_mem, 0))
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@@ -4604,43 +4599,7 @@ _int_realloc(mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
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}
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else
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{
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- /*
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- Unroll copy of <= 36 bytes (72 if 8byte sizes)
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- We know that contents have an odd number of
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- INTERNAL_SIZE_T-sized words; minimally 3.
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- */
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-
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- copysize = oldsize - SIZE_SZ;
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- s = (INTERNAL_SIZE_T *) (chunk2mem (oldp));
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- d = (INTERNAL_SIZE_T *) (newmem);
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- ncopies = copysize / sizeof (INTERNAL_SIZE_T);
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- assert (ncopies >= 3);
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-
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- if (ncopies > 9)
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- memcpy (d, s, copysize);
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-
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- else
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- {
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- *(d + 0) = *(s + 0);
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- *(d + 1) = *(s + 1);
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- *(d + 2) = *(s + 2);
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- if (ncopies > 4)
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- {
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- *(d + 3) = *(s + 3);
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- *(d + 4) = *(s + 4);
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- if (ncopies > 6)
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- {
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- *(d + 5) = *(s + 5);
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- *(d + 6) = *(s + 6);
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- if (ncopies > 8)
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- {
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- *(d + 7) = *(s + 7);
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- *(d + 8) = *(s + 8);
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- }
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- }
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- }
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- }
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-
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+ memcpy (newmem, chunk2mem (oldp), oldsize - SIZE_SZ);
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_int_free (av, oldp, 1);
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check_inuse_chunk (av, newp);
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return chunk2mem (newp);
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