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| author | Rich Felker <dalias@aerifal.cx> | 2011-08-15 01:59:15 -0400 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2011-08-15 01:59:15 -0400 |
| commit | ce7c6341d38ecd3af4d1e01032e9ea8b4078aa97 (patch) | |
| tree | e7b6fdc92a1a60a85d0c3c45a46224e9782f9acb | |
| parent | 6cb277d75e07557dd8442202722d280c1bf93c08 (diff) | |
| download | musl-ce7c6341d38ecd3af4d1e01032e9ea8b4078aa97.tar.gz musl-ce7c6341d38ecd3af4d1e01032e9ea8b4078aa97.tar.bz2 musl-ce7c6341d38ecd3af4d1e01032e9ea8b4078aa97.tar.xz musl-ce7c6341d38ecd3af4d1e01032e9ea8b4078aa97.zip | |
simplify and improve double-free check
a valid mmapped block will have an even (actually aligned) "extra"
field, whereas a freed chunk on the heap will always have an in-use
neighbor.
this fixes a potential bug if mmap ever allocated memory below the
main program/brk (in which case it would be wrongly-detected as a
double-free by the old code) and allows the double-free check to work
for donated memory outside of the brk area (or, in the future,
secondary heap zones if support for their creation is added).
| -rw-r--r-- | src/malloc/malloc.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c index db4287ef..0888afa9 100644 --- a/src/malloc/malloc.c +++ b/src/malloc/malloc.c @@ -394,7 +394,7 @@ void *realloc(void *p, size_t n) size_t oldlen = n0 + extra; size_t newlen = n + extra; /* Crash on realloc of freed chunk */ - if ((uintptr_t)base < mal.brk) *(volatile char *)0=0; + if (extra & 1) *(volatile char *)0=0; if (newlen < PAGE_SIZE && (new = malloc(n))) { memcpy(new, p, n-OVERHEAD); free(p); @@ -457,7 +457,7 @@ void free(void *p) char *base = (char *)self - extra; size_t len = CHUNK_SIZE(self) + extra; /* Crash on double free */ - if ((uintptr_t)base < mal.brk) *(volatile char *)0=0; + if (extra & 1) *(volatile char *)0=0; __munmap(base, len); return; } |