--- /dev/null
+From cd57953936f2213dfaccce10d20f396956222c7d Mon Sep 17 00:00:00 2001
+From: Vasily Gorbik <gor@linux.ibm.com>
+Date: Wed, 1 Mar 2023 17:58:06 +0100
+Subject: s390/kprobes: fix current_kprobe never cleared after kprobes reenter
+
+From: Vasily Gorbik <gor@linux.ibm.com>
+
+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>
+---
+ arch/s390/kernel/kprobes.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+--- a/arch/s390/kernel/kprobes.c
++++ b/arch/s390/kernel/kprobes.c
+@@ -272,6 +272,7 @@ static void pop_kprobe(struct kprobe_ctl
+ {
+ __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);
+
--- /dev/null
+From 42e19e6f04984088b6f9f0507c4c89a8152d9730 Mon Sep 17 00:00:00 2001
+From: Vasily Gorbik <gor@linux.ibm.com>
+Date: Wed, 1 Mar 2023 02:23:08 +0100
+Subject: s390/kprobes: fix irq mask clobbering on kprobe reenter from post_handler
+
+From: Vasily Gorbik <gor@linux.ibm.com>
+
+commit 42e19e6f04984088b6f9f0507c4c89a8152d9730 upstream.
+
+Recent test_kprobe_missed kprobes kunit test uncovers the following error
+(reported when CONFIG_DEBUG_ATOMIC_SLEEP is enabled):
+
+BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580
+in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 662, name: kunit_try_catch
+preempt_count: 0, expected: 0
+RCU nest depth: 0, expected: 0
+no locks held by kunit_try_catch/662.
+irq event stamp: 280
+hardirqs last enabled at (279): [<00000003e60a3d42>] __do_pgm_check+0x17a/0x1c0
+hardirqs last disabled at (280): [<00000003e3bd774a>] kprobe_exceptions_notify+0x27a/0x318
+softirqs last enabled at (0): [<00000003e3c5c890>] copy_process+0x14a8/0x4c80
+softirqs last disabled at (0): [<0000000000000000>] 0x0
+CPU: 46 PID: 662 Comm: kunit_try_catch Tainted: G N 6.2.0-173644-g44c18d77f0c0 #2
+Hardware name: IBM 3931 A01 704 (LPAR)
+Call Trace:
+ [<00000003e60a3a00>] dump_stack_lvl+0x120/0x198
+ [<00000003e3d02e82>] __might_resched+0x60a/0x668
+ [<00000003e60b9908>] __mutex_lock+0xc0/0x14e0
+ [<00000003e60bad5a>] mutex_lock_nested+0x32/0x40
+ [<00000003e3f7b460>] unregister_kprobe+0x30/0xd8
+ [<00000003e51b2602>] test_kprobe_missed+0xf2/0x268
+ [<00000003e51b5406>] kunit_try_run_case+0x10e/0x290
+ [<00000003e51b7dfa>] kunit_generic_run_threadfn_adapter+0x62/0xb8
+ [<00000003e3ce30f8>] kthread+0x2d0/0x398
+ [<00000003e3b96afa>] __ret_from_fork+0x8a/0xe8
+ [<00000003e60ccada>] ret_from_fork+0xa/0x40
+
+The reason for this error report is that kprobes handling code failed
+to restore irqs.
+
+The problem is that when kprobe is triggered from another kprobe
+post_handler current sequence of enable_singlestep / disable_singlestep
+is the following:
+enable_singlestep <- original kprobe (saves kprobe_saved_imask)
+enable_singlestep <- kprobe triggered from post_handler (clobbers kprobe_saved_imask)
+disable_singlestep <- kprobe triggered from post_handler (restores kprobe_saved_imask)
+disable_singlestep <- original kprobe (restores wrong clobbered kprobe_saved_imask)
+
+There is just one kprobe_ctlblk per cpu and both calls saves and
+loads irq mask to kprobe_saved_imask. To fix the problem simply move
+resume_execution (which calls disable_singlestep) before calling
+post_handler. This also fixes the problem that post_handler is called
+with pt_regs which were not yet adjusted after single-stepping.
+
+Cc: stable@vger.kernel.org
+Fixes: 4ba069b802c2 ("[S390] add kprobes support.")
+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>
+---
+ arch/s390/kernel/kprobes.c | 3 +--
+ 1 file changed, 1 insertion(+), 2 deletions(-)
+
+--- a/arch/s390/kernel/kprobes.c
++++ b/arch/s390/kernel/kprobes.c
+@@ -546,12 +546,11 @@ static int post_kprobe_handler(struct pt
+ if (!p)
+ return 0;
+
++ resume_execution(p, regs);
+ if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ p->post_handler(p, regs, 0);
+ }
+-
+- resume_execution(p, regs);
+ pop_kprobe(kcb);
+ preempt_enable_no_resched();
+
projects / thirdparty / kernel / stable-queue.git / commitdiff
