In kcov_remote_start()/kcov_remote_stop(), we swap the previous KCOV
metadata of the current task into a per-CPU variable. However, the
kcov_mode_enabled(mode) check is not sufficient in the case of remote
KCOV coverage: current->kcov_mode always remains KCOV_MODE_DISABLED
for remote KCOV objects.
If the original task that has invoked the KCOV_REMOTE_ENABLE ioctl
happens to get interrupted and kcov_remote_start() is called, it
ultimately leads to kcov_remote_stop() NOT restoring the original
KCOV reference. So when the task exits, all registered remote KCOV
handles remain active forever.
Fix it by introducing a special kcov_mode that is assigned to the
task that owns a KCOV remote object. It makes kcov_mode_enabled()
return true and yet does not trigger coverage collection in
__sanitizer_cov_trace_pc() and write_comp_data().
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Aleksandr Nogikh <nogikh@xxxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Fixes: 5ff3b30ab57d ("kcov: collect coverage from interrupts")
---
Changes v1 -> v2:
* Replaced WRITE_ONCE() with an ordinary assignment.
* Added stable@xxxxxxxxxxxxxxx to the Cc list.
---
include/linux/kcov.h | 2 ++
kernel/kcov.c | 1 +
2 files changed, 3 insertions(+)
diff --git a/include/linux/kcov.h b/include/linux/kcov.h
index b851ba415e03..3b479a3d235a 100644
--- a/include/linux/kcov.h
+++ b/include/linux/kcov.h
@@ -21,6 +21,8 @@ enum kcov_mode {
KCOV_MODE_TRACE_PC = 2,
/* Collecting comparison operands mode. */
KCOV_MODE_TRACE_CMP = 3,
+ /* The process owns a KCOV remote reference. */
+ KCOV_MODE_REMOTE = 4,
};
#define KCOV_IN_CTXSW (1 << 30)
diff --git a/kernel/kcov.c b/kernel/kcov.c
index c3124f6d5536..f0a69d402066 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -632,6 +632,7 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
return -EINVAL;
kcov->mode = mode;
t->kcov = kcov;
+ t->kcov_mode = KCOV_MODE_REMOTE;
kcov->t = t;
kcov->remote = true;
kcov->remote_size = remote_arg->area_size;
--
2.45.2.627.g7a2c4fd464-goog
