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 <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>
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index f66da02..4e2ec19 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -269,6 +269,23 @@
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 bf4dcca..3da76ad 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2126,6 +2126,29 @@
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 fe9314a..b734ca4 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -38,15 +38,12 @@
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 946ed45..868f1bc 100644
--- a/kernel/time/timer_stats.c
+++ b/kernel/time/timer_stats.c
@@ -257,14 +257,12 @@
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)