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authorAndrey Konovalov <andreyknvl@google.com>2020-06-10 18:41:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-10 19:14:17 -0700
commit3021e69219e2f3df6d01243000db32d1325cdd0d (patch)
tree48c28c2a05d00a3b3bdc0231960457638653884c /kernel
parent405906600a33a37e225817c085b1807ad46784b4 (diff)
downloadlinux-3021e69219e2f3df6d01243000db32d1325cdd0d.tar.bz2
kcov: check kcov_softirq in kcov_remote_stop()
kcov_remote_stop() should check that the corresponding kcov_remote_start() actually found the specified remote handle and started collecting coverage. This is done by checking the per thread kcov_softirq flag. A particular failure scenario where this was observed involved a softirq with a remote coverage collection section coming between check_kcov_mode() and the access to t->kcov_area in __sanitizer_cov_trace_pc(). In that softirq kcov_remote_start() bailed out after kcov_remote_find() check, but the matching kcov_remote_stop() didn't check if kcov_remote_start() succeeded, and overwrote per thread kcov parameters with invalid (zero) values. Fixes: 5ff3b30ab57d ("kcov: collect coverage from interrupts") Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Marco Elver <elver@google.com> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Link: http://lkml.kernel.org/r/fcd1cd16eac1d2c01a66befd8ea4afc6f8d09833.1591576806.git.andreyknvl@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/kcov.c26
1 files changed, 18 insertions, 8 deletions
diff --git a/kernel/kcov.c b/kernel/kcov.c
index 55c5d883a93e..6afae0bcbac4 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -427,7 +427,8 @@ void kcov_task_exit(struct task_struct *t)
* WARN_ON(!kcov->remote && kcov->t != t);
*
* For KCOV_REMOTE_ENABLE devices, the exiting task is either:
- * 2. A remote task between kcov_remote_start() and kcov_remote_stop().
+ *
+ * 1. A remote task between kcov_remote_start() and kcov_remote_stop().
* In this case we should print a warning right away, since a task
* shouldn't be exiting when it's in a kcov coverage collection
* section. Here t points to the task that is collecting remote
@@ -437,7 +438,7 @@ void kcov_task_exit(struct task_struct *t)
* WARN_ON(kcov->remote && kcov->t != t);
*
* 2. The task that created kcov exiting without calling KCOV_DISABLE,
- * and then again we can make sure that t->kcov->t == t:
+ * and then again we make sure that t->kcov->t == t:
* WARN_ON(kcov->remote && kcov->t != t);
*
* By combining all three checks into one we get:
@@ -764,7 +765,7 @@ static const struct file_operations kcov_fops = {
* Internally, kcov_remote_start() looks up the kcov device associated with the
* provided handle, allocates an area for coverage collection, and saves the
* pointers to kcov and area into the current task_struct to allow coverage to
- * be collected via __sanitizer_cov_trace_pc()
+ * be collected via __sanitizer_cov_trace_pc().
* In turns kcov_remote_stop() clears those pointers from task_struct to stop
* collecting coverage and copies all collected coverage into the kcov area.
*/
@@ -972,16 +973,25 @@ void kcov_remote_stop(void)
local_irq_restore(flags);
return;
}
- kcov = t->kcov;
- area = t->kcov_area;
- size = t->kcov_size;
- sequence = t->kcov_sequence;
-
+ /*
+ * When in softirq, check if the corresponding kcov_remote_start()
+ * actually found the remote handle and started collecting coverage.
+ */
+ if (in_serving_softirq() && !t->kcov_softirq) {
+ local_irq_restore(flags);
+ return;
+ }
+ /* Make sure that kcov_softirq is only set when in softirq. */
if (WARN_ON(!in_serving_softirq() && t->kcov_softirq)) {
local_irq_restore(flags);
return;
}
+ kcov = t->kcov;
+ area = t->kcov_area;
+ size = t->kcov_size;
+ sequence = t->kcov_sequence;
+
kcov_stop(t);
if (in_serving_softirq()) {
t->kcov_softirq = 0;