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Fix race between cat /proc/*/wchan and rmmod et al

Browse Source 
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 <adobriyan@sw.ru>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2007-05-08 00:28:43 -07:00 committed by Linus Torvalds
parent ffb4512276
commit 9d65cb4a17
7 changed files with 66 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
fs/proc/base.c
View File

@ -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 */

7
include/linux/kallsyms.h
View File

@ -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*/

6
include/linux/module.h
View File

@ -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)

17
kernel/kallsyms.c
View File

@ -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)
{

23
kernel/module.c
View File

@ -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)
{

11
kernel/time/timer_list.c
View File

@ -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

10
kernel/time/timer_stats.c
View File

@ -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)