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commit c0e82f117357a941e4d40fcc08babbd6a3c3a1b5
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Author: Istvan Kurucsai <pistukem@gmail.com>
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Date: Fri Dec 21 00:13:01 2018 -0500
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malloc: Check the alignment of mmapped chunks before unmapping.
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* malloc/malloc.c (munmap_chunk): Verify chunk alignment.
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diff --git a/malloc/malloc.c b/malloc/malloc.c
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index 4df5cb4862a7b854..4412a4ffc83b013b 100644
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--- a/malloc/malloc.c
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+++ b/malloc/malloc.c
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@@ -2817,6 +2817,7 @@ systrim (size_t pad, mstate av)
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static void
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munmap_chunk (mchunkptr p)
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{
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+ size_t pagesize = GLRO (dl_pagesize);
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INTERNAL_SIZE_T size = chunksize (p);
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assert (chunk_is_mmapped (p));
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@@ -2826,6 +2827,7 @@ munmap_chunk (mchunkptr p)
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if (DUMPED_MAIN_ARENA_CHUNK (p))
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return;
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+ uintptr_t mem = (uintptr_t) chunk2mem (p);
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uintptr_t block = (uintptr_t) p - prev_size (p);
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size_t total_size = prev_size (p) + size;
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/* Unfortunately we have to do the compilers job by hand here. Normally
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@@ -2833,7 +2835,8 @@ munmap_chunk (mchunkptr p)
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page size. But gcc does not recognize the optimization possibility
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(in the moment at least) so we combine the two values into one before
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the bit test. */
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- if (__builtin_expect (((block | total_size) & (GLRO (dl_pagesize) - 1)) != 0, 0))
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+ if (__glibc_unlikely ((block | total_size) & (pagesize - 1)) != 0
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+ || __glibc_unlikely (!powerof2 (mem & (pagesize - 1))))
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malloc_printerr ("munmap_chunk(): invalid pointer");
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atomic_decrement (&mp_.n_mmaps);
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