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authorPetr Mladek <pmladek@suse.com>2018-04-16 14:36:47 +0300
committerJiri Kosina <jkosina@suse.cz>2018-04-17 14:42:48 +0300
commit3b2c77d000fe9f7d02e9e726e00dccf9f92b256f (patch)
treee2586a9d55451fecd9e83deadaebefb717fcbbb2 /samples
parente91c2518a5d22a07642f35d85f39001ad379dae4 (diff)
downloadlinux-3b2c77d000fe9f7d02e9e726e00dccf9f92b256f.tar.xz
livepatch: Allow to call a custom callback when freeing shadow variables
We might need to do some actions before the shadow variable is freed. For example, we might need to remove it from a list or free some data that it points to. This is already possible now. The user can get the shadow variable by klp_shadow_get(), do the necessary actions, and then call klp_shadow_free(). This patch allows to do it a more elegant way. The user could implement the needed actions in a callback that is passed to klp_shadow_free() as a parameter. The callback usually does reverse operations to the constructor callback that can be called by klp_shadow_*alloc(). It is especially useful for klp_shadow_free_all(). There we need to do these extra actions for each found shadow variable with the given ID. Note that the memory used by the shadow variable itself is still released later by rcu callback. It is needed to protect internal structures that keep all shadow variables. But the destructor is called immediately. The shadow variable must not be access anyway after klp_shadow_free() is called. The user is responsible to protect this any suitable way. Be aware that the destructor is called under klp_shadow_lock. It is the same as for the contructor in klp_shadow_alloc(). Signed-off-by: Petr Mladek <pmladek@suse.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'samples')
-rw-r--r--samples/livepatch/livepatch-shadow-fix1.c25
-rw-r--r--samples/livepatch/livepatch-shadow-fix2.c27
2 files changed, 31 insertions, 21 deletions
diff --git a/samples/livepatch/livepatch-shadow-fix1.c b/samples/livepatch/livepatch-shadow-fix1.c
index 04151c7f2631..49b13553eaae 100644
--- a/samples/livepatch/livepatch-shadow-fix1.c
+++ b/samples/livepatch/livepatch-shadow-fix1.c
@@ -98,9 +98,19 @@ struct dummy *livepatch_fix1_dummy_alloc(void)
return d;
}
+static void livepatch_fix1_dummy_leak_dtor(void *obj, void *shadow_data)
+{
+ void *d = obj;
+ void **shadow_leak = shadow_data;
+
+ kfree(*shadow_leak);
+ pr_info("%s: dummy @ %p, prevented leak @ %p\n",
+ __func__, d, *shadow_leak);
+}
+
void livepatch_fix1_dummy_free(struct dummy *d)
{
- void **shadow_leak, *leak;
+ void **shadow_leak;
/*
* Patch: fetch the saved SV_LEAK shadow variable, detach and
@@ -109,15 +119,10 @@ void livepatch_fix1_dummy_free(struct dummy *d)
* was loaded.)
*/
shadow_leak = klp_shadow_get(d, SV_LEAK);
- if (shadow_leak) {
- leak = *shadow_leak;
- klp_shadow_free(d, SV_LEAK);
- kfree(leak);
- pr_info("%s: dummy @ %p, prevented leak @ %p\n",
- __func__, d, leak);
- } else {
+ if (shadow_leak)
+ klp_shadow_free(d, SV_LEAK, livepatch_fix1_dummy_leak_dtor);
+ else
pr_info("%s: dummy @ %p leaked!\n", __func__, d);
- }
kfree(d);
}
@@ -163,7 +168,7 @@ static int livepatch_shadow_fix1_init(void)
static void livepatch_shadow_fix1_exit(void)
{
/* Cleanup any existing SV_LEAK shadow variables */
- klp_shadow_free_all(SV_LEAK);
+ klp_shadow_free_all(SV_LEAK, livepatch_fix1_dummy_leak_dtor);
WARN_ON(klp_unregister_patch(&patch));
}
diff --git a/samples/livepatch/livepatch-shadow-fix2.c b/samples/livepatch/livepatch-shadow-fix2.c
index d6c62844dc15..b34c7bf83356 100644
--- a/samples/livepatch/livepatch-shadow-fix2.c
+++ b/samples/livepatch/livepatch-shadow-fix2.c
@@ -68,22 +68,27 @@ bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
return time_after(jiffies, d->jiffies_expire);
}
+static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
+{
+ void *d = obj;
+ void **shadow_leak = shadow_data;
+
+ kfree(*shadow_leak);
+ pr_info("%s: dummy @ %p, prevented leak @ %p\n",
+ __func__, d, *shadow_leak);
+}
+
void livepatch_fix2_dummy_free(struct dummy *d)
{
- void **shadow_leak, *leak;
+ void **shadow_leak;
int *shadow_count;
/* Patch: copy the memory leak patch from the fix1 module. */
shadow_leak = klp_shadow_get(d, SV_LEAK);
- if (shadow_leak) {
- leak = *shadow_leak;
- klp_shadow_free(d, SV_LEAK);
- kfree(leak);
- pr_info("%s: dummy @ %p, prevented leak @ %p\n",
- __func__, d, leak);
- } else {
+ if (shadow_leak)
+ klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
+ else
pr_info("%s: dummy @ %p leaked!\n", __func__, d);
- }
/*
* Patch: fetch the SV_COUNTER shadow variable and display
@@ -93,7 +98,7 @@ void livepatch_fix2_dummy_free(struct dummy *d)
if (shadow_count) {
pr_info("%s: dummy @ %p, check counter = %d\n",
__func__, d, *shadow_count);
- klp_shadow_free(d, SV_COUNTER);
+ klp_shadow_free(d, SV_COUNTER, NULL);
}
kfree(d);
@@ -140,7 +145,7 @@ static int livepatch_shadow_fix2_init(void)
static void livepatch_shadow_fix2_exit(void)
{
/* Cleanup any existing SV_COUNTER shadow variables */
- klp_shadow_free_all(SV_COUNTER);
+ klp_shadow_free_all(SV_COUNTER, NULL);
WARN_ON(klp_unregister_patch(&patch));
}