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[random] Suppress UBSan #9060

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[random] Suppress UBSan #9060

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9fe30a1
random: suppress UBSan
zeriyoshi Jul 20, 2022
9eb0ae8
fix: no_sanitize attribute requires GCC 8 or higher
zeriyoshi Jul 20, 2022
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14 changes: 10 additions & 4 deletions ext/random/random.c
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,14 @@

#if __has_feature(memory_sanitizer)
# include <sanitizer/msan_interface.h>
# define MSAN_UNPOISON(ptr, size) __msan_unpoison((ptr), (size));
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@guilliamxavier guilliamxavier Jul 20, 2022 •
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trailing semicolon to remove? (but why touch this part anyway?)

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This is because we initially used a similar macro branch. Revert back to the original.

#else
# define MSAN_UNPOISON(ptr, size)
#endif
#if __has_feature(undefined_behavior_sanitizer) || ZEND_GCC_VERSION >= 8000
# define UBSAN_SUPPRESS_SIGNED_INTEGER_OVERFLOW __attribute__((no_sanitize("signed-integer-overflow")))
#else
# define UBSAN_SUPPRESS_SIGNED_INTEGER_OVERFLOW
#endif

#include "random_arginfo.h"
Expand Down Expand Up @@ -317,7 +325,7 @@ PHPAPI zend_object *php_random_engine_common_clone_object(zend_object *object)
}

/* {{{ php_random_range */
PHPAPI zend_long php_random_range(const php_random_algo *algo, php_random_status *status, zend_long min, zend_long max)
UBSAN_SUPPRESS_SIGNED_INTEGER_OVERFLOW PHPAPI zend_long php_random_range(const php_random_algo *algo, php_random_status *status, zend_long min, zend_long max)
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Can we not avoid this undefined behavior by using unsigned integers and only then casting them to signed? I think all we might need is:

return (zend_long) (rand_range64(algo, status, umax) + min);

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Related, php_random_int does umax = (zend_ulong) max - (zend_ulong) min;

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@iluuu1994 @guilliamxavier
I had BC break concerns about this, but apparently my fears were unfounded. I will correct it to the appropriate form. Thanks!

$ docker run --rm -it arm64v8/php:8.1-cli -r 'mt_srand(1234); echo mt_rand(PHP_INT_MIN, PHP_INT_MAX) . PHP_EOL;'
-5690461752414248237
$ docker run --rm -it amd64/php:8.1-cli -r 'mt_srand(1234); echo mt_rand(PHP_INT_MIN, PHP_INT_MAX) . PHP_EOL;'
WARNING: The requested image's platform (linux/amd64) does not match the detected host platform (linux/arm64/v8) and no specific platform was requested
-5690461752414248237

{
zend_ulong umax = max - min;

Expand Down Expand Up @@ -539,10 +547,8 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, bool should_throw)
}
}

# if __has_feature(memory_sanitizer)
/* MSan does not instrument manual syscall invocations. */
__msan_unpoison(bytes + read_bytes, n);
# endif
MSAN_UNPOISON(bytes + read_bytes, n);
read_bytes += (size_t) n;
}
# endif
Expand Down