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36 lines
1.2 KiB
36 lines
1.2 KiB
9 months ago
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From b9cde4e3aa1ff338da7064daf1386b2f4a7351ba Mon Sep 17 00:00:00 2001
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From: DJ Delorie <dj@redhat.com>
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Date: Sat, 4 Apr 2020 01:44:56 -0400
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Subject: malloc: ensure set_max_fast never stores zero [BZ #25733]
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The code for set_max_fast() stores an "impossibly small value"
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instead of zero, when the parameter is zero. However, for
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small values of the parameter (ex: 1 or 2) the computation
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results in a zero being stored anyway.
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This patch checks for the parameter being small enough for the
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computation to result in zero instead, so that a zero is never
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stored.
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key values which result in zero being stored:
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x86-64: 1..7 (or other 64-bit)
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i686: 1..11
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armhfp: 1..3 (or other 32-bit)
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Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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diff --git a/malloc/malloc.c b/malloc/malloc.c
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index 6acb5ad43a..ee87ddbbf9 100644
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--- a/malloc/malloc.c
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+++ b/malloc/malloc.c
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@@ -1632,7 +1632,7 @@ static INTERNAL_SIZE_T global_max_fast;
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*/
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#define set_max_fast(s) \
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- global_max_fast = (((s) == 0) \
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+ global_max_fast = (((size_t) (s) <= MALLOC_ALIGN_MASK - SIZE_SZ) \
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? MIN_CHUNK_SIZE / 2 : ((s + SIZE_SZ) & ~MALLOC_ALIGN_MASK))
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static inline INTERNAL_SIZE_T
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