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tracing/user_events: Ensure bit is cleared on unregister 

If an event is enabled and a user process unregisters user_events, the
bit is left set. Fix this by always clearing the bit in the user process
if unregister is successful.

Update abi self-test to ensure this occurs properly.

Link: https://lkml.kernel.org/r/20230425225107.8525-3-beaub@linux.microsoft.com

Suggested-by: Doug Cook <dcook@linux.microsoft.com>
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Beau Belgrave 2023-04-25 15:51:05 -07:00 committed by Steven Rostedt (Google)
parent cd98c93286
commit 17b439db21
2 changed files with 40 additions and 3 deletions
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34
kernel/trace/trace_events_user.c
View File

@ -2149,6 +2149,35 @@ static long user_unreg_get(struct user_unreg __user *ureg,
return ret;
}
static int user_event_mm_clear_bit(struct user_event_mm *user_mm,
unsigned long uaddr, unsigned char bit)
{
struct user_event_enabler enabler;
int result;
memset(&enabler, 0, sizeof(enabler));
enabler.addr = uaddr;
enabler.values = bit;
retry:
/* Prevents state changes from racing with new enablers */
mutex_lock(&event_mutex);
/* Force the bit to be cleared, since no event is attached */
mmap_read_lock(user_mm->mm);
result = user_event_enabler_write(user_mm, &enabler, false);
mmap_read_unlock(user_mm->mm);
mutex_unlock(&event_mutex);
if (result) {
/* Attempt to fault-in and retry if it worked */
if (!user_event_mm_fault_in(user_mm, uaddr))
goto retry;
}
return result;
}
/*
* Unregisters an enablement address/bit within a task/user mm.
*/
@ -2193,6 +2222,11 @@ static long user_events_ioctl_unreg(unsigned long uarg)
mutex_unlock(&event_mutex);
/* Ensure bit is now cleared for user, regardless of event status */
if (!ret)
ret = user_event_mm_clear_bit(mm, reg.disable_addr,
reg.disable_bit);
return ret;
}

9
tools/testing/selftests/user_events/abi_test.c
View File

@ -109,13 +109,16 @@ TEST_F(user, enablement) {
ASSERT_EQ(0, change_event(false));
ASSERT_EQ(0, self->check);
/* Should not change after disable */
/* Ensure kernel clears bit after disable */
ASSERT_EQ(0, change_event(true));
ASSERT_EQ(1, self->check);
ASSERT_EQ(0, reg_disable(&self->check, 0));
ASSERT_EQ(0, self->check);
/* Ensure doesn't change after unreg */
ASSERT_EQ(0, change_event(true));
ASSERT_EQ(0, self->check);
ASSERT_EQ(0, change_event(false));
ASSERT_EQ(1, self->check);
self->check = 0;
}
TEST_F(user, bit_sizes) {