From 9d65cb4a1718a072898c7a57a3bc61b2dc4bcd4d Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Tue, 8 May 2007 00:28:43 -0700 Subject: [PATCH] Fix race between cat /proc/*/wchan and rmmod et al kallsyms_lookup() can go iterating over modules list unprotected which is OK for emergency situations (oops), but not OK for regular stuff like /proc/*/wchan. Introduce lookup_symbol_name()/lookup_module_symbol_name() which copy symbol name into caller-supplied buffer or return -ERANGE. All copying is done with module_mutex held, so... Signed-off-by: Alexey Dobriyan Cc: Rusty Russell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/base.c | 11 +++++------ include/linux/kallsyms.h | 7 +++++++ include/linux/module.h | 6 ++++++ kernel/kallsyms.c | 17 +++++++++++++++++ kernel/module.c | 23 +++++++++++++++++++++++ kernel/time/timer_list.c | 11 ++++------- kernel/time/timer_stats.c | 10 ++++------ 7 files changed, 66 insertions(+), 19 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 3b4fe21c7e9..0c2052c7924 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -278,16 +278,15 @@ static int proc_pid_auxv(struct task_struct *task, char *buffer) */ static int proc_pid_wchan(struct task_struct *task, char *buffer) { - const char *sym_name; unsigned long wchan; - char namebuf[KSYM_NAME_LEN+1]; + char symname[KSYM_NAME_LEN+1]; wchan = get_wchan(task); - sym_name = kallsyms_lookup(wchan, NULL, NULL, NULL, namebuf); - if (sym_name) - return sprintf(buffer, "%s", sym_name); - return sprintf(buffer, "%lu", wchan); + if (lookup_symbol_name(wchan, symname) < 0) + return sprintf(buffer, "%lu", wchan); + else + return sprintf(buffer, "%s", symname); } #endif /* CONFIG_KALLSYMS */ diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h index 3e3b92dabe3..ae0117a95cf 100644 --- a/include/linux/kallsyms.h +++ b/include/linux/kallsyms.h @@ -30,6 +30,8 @@ extern int sprint_symbol(char *buffer, unsigned long address); /* Look up a kernel symbol and print it to the kernel messages. */ extern void __print_symbol(const char *fmt, unsigned long address); +int lookup_symbol_name(unsigned long addr, char *symname); + #else /* !CONFIG_KALLSYMS */ static inline unsigned long kallsyms_lookup_name(const char *name) @@ -58,6 +60,11 @@ static inline int sprint_symbol(char *buffer, unsigned long addr) return 0; } +static inline int lookup_symbol_name(unsigned long addr, char *symname) +{ + return -ERANGE; +} + /* Stupid that this does nothing, but I didn't create this mess. */ #define __print_symbol(fmt, addr) #endif /*CONFIG_KALLSYMS*/ diff --git a/include/linux/module.h b/include/linux/module.h index 58d5a10cdf0..099ae5932c6 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -454,6 +454,7 @@ const char *module_address_lookup(unsigned long addr, unsigned long *symbolsize, unsigned long *offset, char **modname); +int lookup_module_symbol_name(unsigned long addr, char *symname); /* For extable.c to search modules' exception tables. */ const struct exception_table_entry *search_module_extables(unsigned long addr); @@ -525,6 +526,11 @@ static inline const char *module_address_lookup(unsigned long addr, return NULL; } +static inline int lookup_module_symbol_name(unsigned long addr, char *symname) +{ + return -ERANGE; +} + static inline int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type, char *name, char *module_name, int *exported) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index f66da025cb7..4e2ec191a12 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -269,6 +269,23 @@ const char *kallsyms_lookup(unsigned long addr, return NULL; } +int lookup_symbol_name(unsigned long addr, char *symname) +{ + symname[0] = '\0'; + symname[KSYM_NAME_LEN] = '\0'; + + if (is_ksym_addr(addr)) { + unsigned long pos; + + pos = get_symbol_pos(addr, NULL, NULL); + /* Grab name */ + kallsyms_expand_symbol(get_symbol_offset(pos), symname); + return 0; + } + /* see if it's in a module */ + return lookup_module_symbol_name(addr, symname); +} + /* Look up a kernel symbol and return it in a text buffer. */ int sprint_symbol(char *buffer, unsigned long address) { diff --git a/kernel/module.c b/kernel/module.c index bf4dccadf7b..3da76ad32d7 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2126,6 +2126,29 @@ const char *module_address_lookup(unsigned long addr, return NULL; } +int lookup_module_symbol_name(unsigned long addr, char *symname) +{ + struct module *mod; + + mutex_lock(&module_mutex); + list_for_each_entry(mod, &modules, list) { + if (within(addr, mod->module_init, mod->init_size) || + within(addr, mod->module_core, mod->core_size)) { + const char *sym; + + sym = get_ksymbol(mod, addr, NULL, NULL); + if (!sym) + goto out; + strlcpy(symname, sym, KSYM_NAME_LEN + 1); + mutex_unlock(&module_mutex); + return 0; + } + } +out: + mutex_unlock(&module_mutex); + return -ERANGE; +} + int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type, char *name, char *module_name, int *exported) { diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c index fe9314a89f2..b734ca4bc75 100644 --- a/kernel/time/timer_list.c +++ b/kernel/time/timer_list.c @@ -38,15 +38,12 @@ DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases); static void print_name_offset(struct seq_file *m, void *sym) { - unsigned long addr = (unsigned long)sym; - char namebuf[KSYM_NAME_LEN+1]; - const char *sym_name; + char symname[KSYM_NAME_LEN+1]; - sym_name = kallsyms_lookup(addr, NULL, NULL, NULL, namebuf); - if (sym_name) - SEQ_printf(m, "%s", sym_name); - else + if (lookup_symbol_name((unsigned long)sym, symname) < 0) SEQ_printf(m, "<%p>", sym); + else + SEQ_printf(m, "%s", symname); } static void diff --git a/kernel/time/timer_stats.c b/kernel/time/timer_stats.c index 946ed45f7d2..868f1bceb07 100644 --- a/kernel/time/timer_stats.c +++ b/kernel/time/timer_stats.c @@ -257,14 +257,12 @@ void timer_stats_update_stats(void *timer, pid_t pid, void *startf, static void print_name_offset(struct seq_file *m, unsigned long addr) { - char namebuf[KSYM_NAME_LEN+1]; - const char *sym_name; + char symname[KSYM_NAME_LEN+1]; - sym_name = kallsyms_lookup(addr, NULL, NULL, NULL, namebuf); - if (sym_name) - seq_printf(m, "%s", sym_name); - else + if (lookup_symbol_name(addr, symname) < 0) seq_printf(m, "<%p>", (void *)addr); + else + seq_printf(m, "%s", symname); } static int tstats_show(struct seq_file *m, void *v)