From: Sam James Date: Tue, 10 Dec 2024 01:21:46 +0000 (+0000) Subject: stdlib: random_r: fix unaligned access in initstate and initstate_r [BZ #30584] X-Git-Tag: glibc-2.41~161 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d5bceac99d24af1131b90027dab267e437b65cd1;p=thirdparty%2Fglibc.git stdlib: random_r: fix unaligned access in initstate and initstate_r [BZ #30584] The initstate{,_r} interfaces are documented in BSD as needing an aligned array of 32-bit values, but neither POSIX nor glibc's own documentation require it to be aligned. glibc's documentation says it "should" be a power of 2, but not must. Use memcpy to read and write to `state` to handle such an unaligned argument. Co-authored-by: Adhemerval Zanella Reviewed-by: Florian Weimer --- diff --git a/stdlib/Makefile b/stdlib/Makefile index cad1a2e244..374643e753 100644 --- a/stdlib/Makefile +++ b/stdlib/Makefile @@ -300,6 +300,7 @@ tests := \ tst-rand48-2 \ tst-random \ tst-random2 \ + tst-random-bz30584 \ tst-realpath \ tst-realpath-toolong \ tst-secure-getenv \ diff --git a/stdlib/random_r.c b/stdlib/random_r.c index c37284c82d..605e96983c 100644 --- a/stdlib/random_r.c +++ b/stdlib/random_r.c @@ -55,6 +55,7 @@ #include #include #include +#include /* An improved random number generation package. In addition to the standard @@ -146,7 +147,21 @@ static const struct random_poly_info random_poly_info = { DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 } }; +static inline int32_t +read_state (int32_t *b, int idx) +{ + int32_t r; + memcpy (&r, (char *) b + idx * 4, sizeof (int32_t)); + return r; +} +static inline void +write_state (int32_t *b, int idx, int32_t v) +{ + /* Use literal 4 to avoid conversion to an unsigned type and pointer + wraparound. */ + memcpy ((char *) b + idx * 4, &v, 4); +} /* Initialize the random number generator based on the given seed. If the @@ -177,7 +192,7 @@ __srandom_r (unsigned int seed, struct random_data *buf) /* We must make sure the seed is not 0. Take arbitrarily 1 in this case. */ if (seed == 0) seed = 1; - state[0] = seed; + write_state (state, 0, seed); if (type == TYPE_0) goto done; @@ -194,7 +209,7 @@ __srandom_r (unsigned int seed, struct random_data *buf) word = 16807 * lo - 2836 * hi; if (word < 0) word += 2147483647; - *++dst = word; + write_state (++dst, 0, word); } buf->fptr = &state[buf->rand_sep]; @@ -238,9 +253,10 @@ __initstate_r (unsigned int seed, char *arg_state, size_t n, { int old_type = buf->rand_type; if (old_type == TYPE_0) - old_state[-1] = TYPE_0; + write_state (old_state, -1, TYPE_0); else - old_state[-1] = (MAX_TYPES * (buf->rptr - old_state)) + old_type; + write_state (old_state, -1, (MAX_TYPES * (buf->rptr - old_state)) + + old_type); } int type; @@ -270,9 +286,9 @@ __initstate_r (unsigned int seed, char *arg_state, size_t n, __srandom_r (seed, buf); - state[-1] = TYPE_0; + write_state (state, -1, TYPE_0); if (type != TYPE_0) - state[-1] = (buf->rptr - state) * MAX_TYPES + type; + write_state (state, -1, (buf->rptr - state) * MAX_TYPES + type); return 0; @@ -307,9 +323,10 @@ __setstate_r (char *arg_state, struct random_data *buf) old_type = buf->rand_type; old_state = buf->state; if (old_type == TYPE_0) - old_state[-1] = TYPE_0; + write_state (old_state, -1, TYPE_0); else - old_state[-1] = (MAX_TYPES * (buf->rptr - old_state)) + old_type; + write_state (old_state, -1, (MAX_TYPES * (buf->rptr - old_state)) + + old_type); type = new_state[-1] % MAX_TYPES; if (type < TYPE_0 || type > TYPE_4) @@ -361,8 +378,9 @@ __random_r (struct random_data *buf, int32_t *result) if (buf->rand_type == TYPE_0) { - int32_t val = ((state[0] * 1103515245U) + 12345U) & 0x7fffffff; - state[0] = val; + int32_t val = ((read_state(state, 0) * 1103515245U) + 12345U) + & 0x7fffffff; + write_state (state, 0, val); *result = val; } else @@ -372,7 +390,9 @@ __random_r (struct random_data *buf, int32_t *result) int32_t *end_ptr = buf->end_ptr; uint32_t val; - val = *fptr += (uint32_t) *rptr; + val = read_state (rptr, 0); + int32_t t = read_state (fptr, 0); + write_state (fptr, 0, t + val); /* Chucking least random bit. */ *result = val >> 1; ++fptr; diff --git a/stdlib/tst-random-bz30584.c b/stdlib/tst-random-bz30584.c new file mode 100644 index 0000000000..0a9b013f26 --- /dev/null +++ b/stdlib/tst-random-bz30584.c @@ -0,0 +1,38 @@ +/* Test program for initstate(), initstate_r() for BZ #30584. + Copyright (C) 2024 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public License as + published by the Free Software Foundation; either version 2.1 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; see the file COPYING.LIB. If + not, see . */ + +#include +#include + +static int +do_test (void) +{ + struct random_data rand_state = { .state = NULL }; + _Alignas (double) char buf[128 + sizeof (int32_t)]; + + /* Test initstate_r with an unaligned `state` array. */ + initstate_r (time (NULL), buf + 1, sizeof buf, &rand_state); + + /* Ditto initstate. */ + initstate (time (NULL), buf + 1, sizeof buf); + + return 0; +} + +#define TEST_FUNCTION do_test () +#include "../test-skeleton.c"