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author | Florian Weimer <fweimer@redhat.com> | 2018-01-04 12:51:48 +0100 |
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committer | Florian Weimer <fweimer@redhat.com> | 2018-01-04 12:51:48 +0100 |
commit | ea00a80db7c0cd1098f848eccd5d1f34d89b7faf (patch) | |
tree | 7760aa2ece3cdf59fe6257c9c75ada70856763da | |
parent | ab8b49432b302237015d0f44e858c17f92fe3a5b (diff) | |
download | glibc-ea00a80db7c0cd1098f848eccd5d1f34d89b7faf.tar.gz glibc-ea00a80db7c0cd1098f848eccd5d1f34d89b7faf.tar.xz glibc-ea00a80db7c0cd1098f848eccd5d1f34d89b7faf.zip |
Add check_mul_overflow_size_t
Backported from commit 2e0bbbfbf95fc9e22692e93658a6fbdd2d4554da.
-rw-r--r-- | ChangeLog | 4 | ||||
-rw-r--r-- | malloc/malloc-internal.h | 19 |
2 files changed, 23 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog index 4c11b729ce..fff166c11e 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,9 @@ 2018-01-04 Florian Weimer <fweimer@redhat.com> + * malloc/malloc-internal.h (check_mul_overflow_size_t): New. + +2018-01-04 Florian Weimer <fweimer@redhat.com> + * include/libc-pointer-arith.h: New file. 2017-09-01 Florian Weimer <fweimer@redhat.com> diff --git a/malloc/malloc-internal.h b/malloc/malloc-internal.h index de6103d7e1..dbd801a58e 100644 --- a/malloc/malloc-internal.h +++ b/malloc/malloc-internal.h @@ -81,5 +81,24 @@ void __malloc_fork_unlock_parent (void) internal_function attribute_hidden; /* Called in the child process after a fork. */ void __malloc_fork_unlock_child (void) internal_function attribute_hidden; +/* Set *RESULT to LEFT * RIGHT. Return true if the multiplication + overflowed. */ +static inline bool +check_mul_overflow_size_t (size_t left, size_t right, size_t *result) +{ +#if __GNUC__ >= 5 + return __builtin_mul_overflow (left, right, result); +#else + /* size_t is unsigned so the behavior on overflow is defined. */ + *result = left * right; + size_t half_size_t = ((size_t) 1) << (8 * sizeof (size_t) / 2); + if (__glibc_unlikely ((left | right) >= half_size_t)) + { + if (__glibc_unlikely (right != 0 && *result / right != left)) + return true; + } + return false; +#endif +} #endif /* _MALLOC_INTERNAL_H */ |