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| author | Vasily Gorbik <gor@linux.ibm.com> | 2023-03-01 17:58:06 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-03-10 09:34:04 +0100 |
| commit | f9a38f5ecf90f0c8935c3814e3a915c71a3bf045 (patch) | |
| tree | 516eb227a70cfea06db649af7624c85c07689203 /arch/s390 | |
| parent | 70afa77327e00f9d38269055dec300e4b9a002e1 (diff) | |
| download | linux-stable-f9a38f5ecf90f0c8935c3814e3a915c71a3bf045.tar.gz linux-stable-f9a38f5ecf90f0c8935c3814e3a915c71a3bf045.tar.bz2 linux-stable-f9a38f5ecf90f0c8935c3814e3a915c71a3bf045.zip | |
s390/kprobes: fix current_kprobe never cleared after kprobes reenter
commit cd57953936f2213dfaccce10d20f396956222c7d upstream.
Recent test_kprobe_missed kprobes kunit test uncovers the following
problem. Once kprobe is triggered from another kprobe (kprobe reenter),
all future kprobes on this cpu are considered as kprobe reenter, thus
pre_handler and post_handler are not being called and kprobes are counted
as "missed".
Commit b9599798f953 ("[S390] kprobes: activation and deactivation")
introduced a simpler scheme for kprobes (de)activation and status
tracking by using push_kprobe/pop_kprobe, which supposed to work for
both initial kprobe entry as well as kprobe reentry and helps to avoid
handling those two cases differently. The problem is that a sequence of
calls in case of kprobes reenter:
push_kprobe() <- NULL (current_kprobe)
push_kprobe() <- kprobe1 (current_kprobe)
pop_kprobe() -> kprobe1 (current_kprobe)
pop_kprobe() -> kprobe1 (current_kprobe)
leaves "kprobe1" as "current_kprobe" on this cpu, instead of setting it
to NULL. In fact push_kprobe/pop_kprobe can only store a single state
(there is just one prev_kprobe in kprobe_ctlblk). Which is a hack but
sufficient, there is no need to have another prev_kprobe just to store
NULL. To make a simple and backportable fix simply reset "prev_kprobe"
when kprobe is poped from this "stack". No need to worry about
"kprobe_status" in this case, because its value is only checked when
current_kprobe != NULL.
Cc: stable@vger.kernel.org
Fixes: b9599798f953 ("[S390] kprobes: activation and deactivation")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/s390')
| -rw-r--r-- | arch/s390/kernel/kprobes.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c index 1508ce7405e9..6c8872f76fb3 100644 --- a/arch/s390/kernel/kprobes.c +++ b/arch/s390/kernel/kprobes.c @@ -279,6 +279,7 @@ static void pop_kprobe(struct kprobe_ctlblk *kcb) { __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); kcb->kprobe_status = kcb->prev_kprobe.status; + kcb->prev_kprobe.kp = NULL; } NOKPROBE_SYMBOL(pop_kprobe); |