param: fix charp parameters set via sysfs
Impact: fix crash on reading from /sys/module/.../ieee80211_default_rc_algo
The module_param type "charp" simply sets a char * pointer in the
module to the parameter in the commandline string: this is why we keep
the (mangled) module command line around. But when set via sysfs (as
about 11 charp parameters can be) this memory is freed on the way
out of the write(). Future reads hit random mem.
So we kstrdup instead: we have to check we're not in early commandline
parsing, and we have to note when we've used it so we can reliably
kfree the parameter when it's next overwritten, and also on module
unload.
(Thanks to Randy Dunlap for CONFIG_SYSFS=n fixes)
Reported-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Diagnosed-by: Frederic Weisbecker <fweisbec@gmail.com>
Tested-by: Frederic Weisbecker <fweisbec@gmail.com>
Tested-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/kernel/module.c b/kernel/module.c
index f77ac32..b862fdb 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1491,6 +1491,9 @@
/* Module unload stuff */
module_unload_free(mod);
+ /* Free any allocated parameters. */
+ destroy_params(mod->kp, mod->num_kp);
+
/* release any pointers to mcount in this module */
ftrace_release(mod->module_core, mod->core_size);
@@ -1898,8 +1901,7 @@
unsigned int symindex = 0;
unsigned int strindex = 0;
unsigned int modindex, versindex, infoindex, pcpuindex;
- unsigned int num_kp, num_mcount;
- struct kernel_param *kp;
+ unsigned int num_mcount;
struct module *mod;
long err = 0;
void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
@@ -2144,8 +2146,8 @@
/* Now we've got everything in the final locations, we can
* find optional sections. */
- kp = section_objs(hdr, sechdrs, secstrings, "__param", sizeof(*kp),
- &num_kp);
+ mod->kp = section_objs(hdr, sechdrs, secstrings, "__param",
+ sizeof(*mod->kp), &mod->num_kp);
mod->syms = section_objs(hdr, sechdrs, secstrings, "__ksymtab",
sizeof(*mod->syms), &mod->num_syms);
mod->crcs = section_addr(hdr, sechdrs, secstrings, "__kcrctab");
@@ -2291,11 +2293,11 @@
*/
list_add_rcu(&mod->list, &modules);
- err = parse_args(mod->name, mod->args, kp, num_kp, NULL);
+ err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp, NULL);
if (err < 0)
goto unlink;
- err = mod_sysfs_setup(mod, kp, num_kp);
+ err = mod_sysfs_setup(mod, mod->kp, mod->num_kp);
if (err < 0)
goto unlink;
add_sect_attrs(mod, hdr->e_shnum, secstrings, sechdrs);