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Message-ID: <20180416224042.GB3094@brightrain.aerifal.cx>
Date: Mon, 16 Apr 2018 18:40:42 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH 1/2] malloc: fix an over-allocation bug
On Mon, Apr 16, 2018 at 08:54:35PM +0300, Alexander Monakov wrote:
> Fix an instance where realloc code would overallocate by OVERHEAD bytes
> amount. Manually arrange for reuse of memcpy-free-return exit sequence.
> ---
> src/malloc/malloc.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c
> index 9e05e1d6..1af4ae5a 100644
> --- a/src/malloc/malloc.c
> +++ b/src/malloc/malloc.c
> @@ -397,10 +397,9 @@ void *realloc(void *p, size_t n)
> size_t newlen = n + extra;
> /* Crash on realloc of freed chunk */
> if (extra & 1) a_crash();
> - if (newlen < PAGE_SIZE && (new = malloc(n))) {
> - memcpy(new, p, n-OVERHEAD);
> - free(p);
> - return new;
> + if (newlen < PAGE_SIZE && (new = malloc(n-OVERHEAD))) {
> + n0 = n;
> + goto copy_free_ret;
> }
> newlen = (newlen + PAGE_SIZE-1) & -PAGE_SIZE;
> if (oldlen == newlen) return p;
> @@ -443,6 +442,7 @@ copy_realloc:
> /* As a last resort, allocate a new chunk and copy to it. */
> new = malloc(n-OVERHEAD);
> if (!new) return 0;
> +copy_free_ret:
> memcpy(new, p, n0-OVERHEAD);
> free(CHUNK_TO_MEM(self));
> return new;
Looks ok. I've got this queued as submitted.
Rich
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