From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- lib/ts_kmp.c | 168 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 168 insertions(+) create mode 100644 lib/ts_kmp.c (limited to 'lib/ts_kmp.c') diff --git a/lib/ts_kmp.c b/lib/ts_kmp.c new file mode 100644 index 000000000..29466c180 --- /dev/null +++ b/lib/ts_kmp.c @@ -0,0 +1,168 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * lib/ts_kmp.c Knuth-Morris-Pratt text search implementation + * + * Authors: Thomas Graf + * + * ========================================================================== + * + * Implements a linear-time string-matching algorithm due to Knuth, + * Morris, and Pratt [1]. Their algorithm avoids the explicit + * computation of the transition function DELTA altogether. Its + * matching time is O(n), for n being length(text), using just an + * auxiliary function PI[1..m], for m being length(pattern), + * precomputed from the pattern in time O(m). The array PI allows + * the transition function DELTA to be computed efficiently + * "on the fly" as needed. Roughly speaking, for any state + * "q" = 0,1,...,m and any character "a" in SIGMA, the value + * PI["q"] contains the information that is independent of "a" and + * is needed to compute DELTA("q", "a") [2]. Since the array PI + * has only m entries, whereas DELTA has O(m|SIGMA|) entries, we + * save a factor of |SIGMA| in the preprocessing time by computing + * PI rather than DELTA. + * + * [1] Cormen, Leiserson, Rivest, Stein + * Introdcution to Algorithms, 2nd Edition, MIT Press + * [2] See finite automaton theory + */ + +#include +#include +#include +#include +#include + +struct ts_kmp +{ + u8 * pattern; + unsigned int pattern_len; + unsigned int prefix_tbl[]; +}; + +static unsigned int kmp_find(struct ts_config *conf, struct ts_state *state) +{ + struct ts_kmp *kmp = ts_config_priv(conf); + unsigned int i, q = 0, text_len, consumed = state->offset; + const u8 *text; + const int icase = conf->flags & TS_IGNORECASE; + + for (;;) { + text_len = conf->get_next_block(consumed, &text, conf, state); + + if (unlikely(text_len == 0)) + break; + + for (i = 0; i < text_len; i++) { + while (q > 0 && kmp->pattern[q] + != (icase ? toupper(text[i]) : text[i])) + q = kmp->prefix_tbl[q - 1]; + if (kmp->pattern[q] + == (icase ? toupper(text[i]) : text[i])) + q++; + if (unlikely(q == kmp->pattern_len)) { + state->offset = consumed + i + 1; + return state->offset - kmp->pattern_len; + } + } + + consumed += text_len; + } + + return UINT_MAX; +} + +static inline void compute_prefix_tbl(const u8 *pattern, unsigned int len, + unsigned int *prefix_tbl, int flags) +{ + unsigned int k, q; + const u8 icase = flags & TS_IGNORECASE; + + for (k = 0, q = 1; q < len; q++) { + while (k > 0 && (icase ? toupper(pattern[k]) : pattern[k]) + != (icase ? toupper(pattern[q]) : pattern[q])) + k = prefix_tbl[k-1]; + if ((icase ? toupper(pattern[k]) : pattern[k]) + == (icase ? toupper(pattern[q]) : pattern[q])) + k++; + prefix_tbl[q] = k; + } +} + +static struct ts_config *kmp_init(const void *pattern, unsigned int len, + gfp_t gfp_mask, int flags) +{ + struct ts_config *conf; + struct ts_kmp *kmp; + int i; + unsigned int prefix_tbl_len; + size_t priv_size; + + /* Zero-length patterns would make kmp_find() read beyond kmp->pattern. */ + if (unlikely(!len)) + return ERR_PTR(-EINVAL); + + /* + * kmp->pattern is stored immediately after the prefix_tbl[] table. + * Reject lengths that would wrap while sizing either region. + */ + if (unlikely(check_mul_overflow(len, sizeof(*kmp->prefix_tbl), + &prefix_tbl_len) || + check_add_overflow(sizeof(*kmp), (size_t)len, &priv_size) || + check_add_overflow(priv_size, prefix_tbl_len, &priv_size))) + return ERR_PTR(-EINVAL); + + conf = alloc_ts_config(priv_size, gfp_mask); + if (IS_ERR(conf)) + return conf; + + conf->flags = flags; + kmp = ts_config_priv(conf); + kmp->pattern_len = len; + compute_prefix_tbl(pattern, len, kmp->prefix_tbl, flags); + kmp->pattern = (u8 *) kmp->prefix_tbl + prefix_tbl_len; + if (flags & TS_IGNORECASE) + for (i = 0; i < len; i++) + kmp->pattern[i] = toupper(((u8 *)pattern)[i]); + else + memcpy(kmp->pattern, pattern, len); + + return conf; +} + +static void *kmp_get_pattern(struct ts_config *conf) +{ + struct ts_kmp *kmp = ts_config_priv(conf); + return kmp->pattern; +} + +static unsigned int kmp_get_pattern_len(struct ts_config *conf) +{ + struct ts_kmp *kmp = ts_config_priv(conf); + return kmp->pattern_len; +} + +static struct ts_ops kmp_ops = { + .name = "kmp", + .find = kmp_find, + .init = kmp_init, + .get_pattern = kmp_get_pattern, + .get_pattern_len = kmp_get_pattern_len, + .owner = THIS_MODULE, + .list = LIST_HEAD_INIT(kmp_ops.list) +}; + +static int __init init_kmp(void) +{ + return textsearch_register(&kmp_ops); +} + +static void __exit exit_kmp(void) +{ + textsearch_unregister(&kmp_ops); +} + +MODULE_DESCRIPTION("Knuth-Morris-Pratt text search implementation"); +MODULE_LICENSE("GPL"); + +module_init(init_kmp); +module_exit(exit_kmp); -- cgit v1.3.1