From d24fa977eec53399a9a49a2e1dc592430ea0a607 Mon Sep 17 00:00:00 2001 From: "Masami Hiramatsu (Google)" Date: Sun, 30 Mar 2025 12:34:47 +0900 Subject: tracing: fprobe: Fix to lock module while registering fprobe Since register_fprobe() does not get the module reference count while registering fgraph filter, if the target functions (symbols) are in modules, those modules can be unloaded when registering fprobe to fgraph. To avoid this issue, get the reference counter of module for each symbol, and put it after register the fprobe. Link: https://lore.kernel.org/all/174330568792.459674.16874380163991113156.stgit@devnote2/ Reported-by: Steven Rostedt Closes: https://lore.kernel.org/all/20250325130628.3a9e234c@gandalf.local.home/ Fixes: 4346ba160409 ("fprobe: Rewrite fprobe on function-graph tracer") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/fprobe.c | 67 ++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 48 insertions(+), 19 deletions(-) (limited to 'kernel/trace/fprobe.c') diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 33082c4e8154..cb86f90d4b1e 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -445,6 +445,7 @@ struct filter_match_data { size_t index; size_t size; unsigned long *addrs; + struct module **mods; }; static int filter_match_callback(void *data, const char *name, unsigned long addr) @@ -458,30 +459,47 @@ static int filter_match_callback(void *data, const char *name, unsigned long add if (!ftrace_location(addr)) return 0; - if (match->addrs) - match->addrs[match->index] = addr; + if (match->addrs) { + struct module *mod = __module_text_address(addr); + + if (mod && !try_module_get(mod)) + return 0; + match->mods[match->index] = mod; + match->addrs[match->index] = addr; + } match->index++; return match->index == match->size; } /* * Make IP list from the filter/no-filter glob patterns. - * Return the number of matched symbols, or -ENOENT. + * Return the number of matched symbols, or errno. + * If @addrs == NULL, this just counts the number of matched symbols. If @addrs + * is passed with an array, we need to pass the an @mods array of the same size + * to increment the module refcount for each symbol. + * This means we also need to call `module_put` for each element of @mods after + * using the @addrs. */ -static int ip_list_from_filter(const char *filter, const char *notfilter, - unsigned long *addrs, size_t size) +static int get_ips_from_filter(const char *filter, const char *notfilter, + unsigned long *addrs, struct module **mods, + size_t size) { struct filter_match_data match = { .filter = filter, .notfilter = notfilter, - .index = 0, .size = size, .addrs = addrs}; + .index = 0, .size = size, .addrs = addrs, .mods = mods}; int ret; + if (addrs && !mods) + return -EINVAL; + ret = kallsyms_on_each_symbol(filter_match_callback, &match); if (ret < 0) return ret; - ret = module_kallsyms_on_each_symbol(NULL, filter_match_callback, &match); - if (ret < 0) - return ret; + if (IS_ENABLED(CONFIG_MODULES)) { + ret = module_kallsyms_on_each_symbol(NULL, filter_match_callback, &match); + if (ret < 0) + return ret; + } return match.index ?: -ENOENT; } @@ -543,24 +561,35 @@ static int fprobe_init(struct fprobe *fp, unsigned long *addrs, int num) */ int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter) { - unsigned long *addrs; - int ret; + unsigned long *addrs __free(kfree) = NULL; + struct module **mods __free(kfree) = NULL; + int ret, num; if (!fp || !filter) return -EINVAL; - ret = ip_list_from_filter(filter, notfilter, NULL, FPROBE_IPS_MAX); - if (ret < 0) - return ret; + num = get_ips_from_filter(filter, notfilter, NULL, NULL, FPROBE_IPS_MAX); + if (num < 0) + return num; - addrs = kcalloc(ret, sizeof(unsigned long), GFP_KERNEL); + addrs = kcalloc(num, sizeof(*addrs), GFP_KERNEL); if (!addrs) return -ENOMEM; - ret = ip_list_from_filter(filter, notfilter, addrs, ret); - if (ret > 0) - ret = register_fprobe_ips(fp, addrs, ret); - kfree(addrs); + mods = kcalloc(num, sizeof(*mods), GFP_KERNEL); + if (!mods) + return -ENOMEM; + + ret = get_ips_from_filter(filter, notfilter, addrs, mods, num); + if (ret < 0) + return ret; + + ret = register_fprobe_ips(fp, addrs, ret); + + for (int i = 0; i < num; i++) { + if (mods[i]) + module_put(mods[i]); + } return ret; } EXPORT_SYMBOL_GPL(register_fprobe); -- cgit v1.2.3 From a3dc2983ca7b90fd35f978502de6d4664d965cfb Mon Sep 17 00:00:00 2001 From: "Masami Hiramatsu (Google)" Date: Tue, 1 Apr 2025 00:35:44 +0900 Subject: tracing: fprobe: Cleanup fprobe hash when module unloading Cleanup fprobe address hash table on module unloading because the target symbols will be disappeared when unloading module and not sure the same symbol is mapped on the same address. Note that this is at least disables the fprobes if a part of target symbols on the unloaded modules. Unlike kprobes, fprobe does not re-enable the probe point by itself. To do that, the caller should take care register/unregister fprobe when loading/unloading modules. This simplifies the fprobe state managememt related to the module loading/unloading. Link: https://lore.kernel.org/all/174343534473.843280.13988101014957210732.stgit@devnote2/ Fixes: 4346ba160409 ("fprobe: Rewrite fprobe on function-graph tracer") Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/fprobe.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 101 insertions(+), 2 deletions(-) (limited to 'kernel/trace/fprobe.c') diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index cb86f90d4b1e..95c6e3473a76 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -89,8 +89,11 @@ static bool delete_fprobe_node(struct fprobe_hlist_node *node) { lockdep_assert_held(&fprobe_mutex); - WRITE_ONCE(node->fp, NULL); - hlist_del_rcu(&node->hlist); + /* Avoid double deleting */ + if (READ_ONCE(node->fp) != NULL) { + WRITE_ONCE(node->fp, NULL); + hlist_del_rcu(&node->hlist); + } return !!find_first_fprobe_node(node->addr); } @@ -411,6 +414,102 @@ static void fprobe_graph_remove_ips(unsigned long *addrs, int num) ftrace_set_filter_ips(&fprobe_graph_ops.ops, addrs, num, 1, 0); } +#ifdef CONFIG_MODULES + +#define FPROBE_IPS_BATCH_INIT 8 +/* instruction pointer address list */ +struct fprobe_addr_list { + int index; + int size; + unsigned long *addrs; +}; + +static int fprobe_addr_list_add(struct fprobe_addr_list *alist, unsigned long addr) +{ + unsigned long *addrs; + + if (alist->index >= alist->size) + return -ENOMEM; + + alist->addrs[alist->index++] = addr; + if (alist->index < alist->size) + return 0; + + /* Expand the address list */ + addrs = kcalloc(alist->size * 2, sizeof(*addrs), GFP_KERNEL); + if (!addrs) + return -ENOMEM; + + memcpy(addrs, alist->addrs, alist->size * sizeof(*addrs)); + alist->size *= 2; + kfree(alist->addrs); + alist->addrs = addrs; + + return 0; +} + +static void fprobe_remove_node_in_module(struct module *mod, struct hlist_head *head, + struct fprobe_addr_list *alist) +{ + struct fprobe_hlist_node *node; + int ret = 0; + + hlist_for_each_entry_rcu(node, head, hlist) { + if (!within_module(node->addr, mod)) + continue; + if (delete_fprobe_node(node)) + continue; + /* + * If failed to update alist, just continue to update hlist. + * Therefore, at list user handler will not hit anymore. + */ + if (!ret) + ret = fprobe_addr_list_add(alist, node->addr); + } +} + +/* Handle module unloading to manage fprobe_ip_table. */ +static int fprobe_module_callback(struct notifier_block *nb, + unsigned long val, void *data) +{ + struct fprobe_addr_list alist = {.size = FPROBE_IPS_BATCH_INIT}; + struct module *mod = data; + int i; + + if (val != MODULE_STATE_GOING) + return NOTIFY_DONE; + + alist.addrs = kcalloc(alist.size, sizeof(*alist.addrs), GFP_KERNEL); + /* If failed to alloc memory, we can not remove ips from hash. */ + if (!alist.addrs) + return NOTIFY_DONE; + + mutex_lock(&fprobe_mutex); + for (i = 0; i < FPROBE_IP_TABLE_SIZE; i++) + fprobe_remove_node_in_module(mod, &fprobe_ip_table[i], &alist); + + if (alist.index < alist.size && alist.index > 0) + ftrace_set_filter_ips(&fprobe_graph_ops.ops, + alist.addrs, alist.index, 1, 0); + mutex_unlock(&fprobe_mutex); + + kfree(alist.addrs); + + return NOTIFY_DONE; +} + +static struct notifier_block fprobe_module_nb = { + .notifier_call = fprobe_module_callback, + .priority = 0, +}; + +static int __init init_fprobe_module(void) +{ + return register_module_notifier(&fprobe_module_nb); +} +early_initcall(init_fprobe_module); +#endif + static int symbols_cmp(const void *a, const void *b) { const char **str_a = (const char **) a; -- cgit v1.2.3