Improve error handling when disarming ftrace-based kprobes. Like with arm_kprobe_ftrace(), propagate any errors from disarm_kprobe_ftrace() so that we do not disable/unregister kprobes that are still armed. In other words, unregister_kprobe() and disable_kprobe() should not report success if the kprobe could not be disarmed.
disarm_all_kprobes() keeps its current behavior and attempts to disarm all kprobes. It returns the last encountered error and gives a warning if not all kprobes could be disarmed. This patch is based on Petr Mladek's original patchset (patches 2 and 3) back in 2015, which improved kprobes error handling, found here: https://lkml.org/lkml/2015/2/26/452 However, further work on this had been paused since then and the patches were not upstreamed. Based-on-patches-by: Petr Mladek <pmla...@suse.com> Acked-by: Masami Hiramatsu <mhira...@kernel.org> Signed-off-by: Jessica Yu <j...@kernel.org> --- kernel/kprobes.c | 76 +++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 51 insertions(+), 25 deletions(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index f4a094007cb5..2d50d3af78d7 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1002,23 +1002,27 @@ static int arm_kprobe_ftrace(struct kprobe *p) } /* Caller must lock kprobe_mutex */ -static void disarm_kprobe_ftrace(struct kprobe *p) +static int disarm_kprobe_ftrace(struct kprobe *p) { - int ret; + int ret = 0; - kprobe_ftrace_enabled--; - if (kprobe_ftrace_enabled == 0) { + if (kprobe_ftrace_enabled == 1) { ret = unregister_ftrace_function(&kprobe_ftrace_ops); - WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret); + if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (%d)\n", ret)) + return ret; } + + kprobe_ftrace_enabled--; + ret = ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 1, 0); WARN(ret < 0, "Failed to disarm kprobe-ftrace at %p (%d)\n", p->addr, ret); + return ret; } #else /* !CONFIG_KPROBES_ON_FTRACE */ #define prepare_kprobe(p) arch_prepare_kprobe(p) #define arm_kprobe_ftrace(p) (0) -#define disarm_kprobe_ftrace(p) do {} while (0) +#define disarm_kprobe_ftrace(p) (0) #endif /* Arm a kprobe with text_mutex */ @@ -1037,18 +1041,18 @@ static int arm_kprobe(struct kprobe *kp) } /* Disarm a kprobe with text_mutex */ -static void disarm_kprobe(struct kprobe *kp, bool reopt) +static int disarm_kprobe(struct kprobe *kp, bool reopt) { - if (unlikely(kprobe_ftrace(kp))) { - disarm_kprobe_ftrace(kp); - return; - } + if (unlikely(kprobe_ftrace(kp))) + return disarm_kprobe_ftrace(kp); cpus_read_lock(); mutex_lock(&text_mutex); __disarm_kprobe(kp, reopt); mutex_unlock(&text_mutex); cpus_read_unlock(); + + return 0; } /* @@ -1629,11 +1633,12 @@ static int aggr_kprobe_disabled(struct kprobe *ap) static struct kprobe *__disable_kprobe(struct kprobe *p) { struct kprobe *orig_p; + int ret; /* Get an original kprobe for return */ orig_p = __get_valid_kprobe(p); if (unlikely(orig_p == NULL)) - return NULL; + return ERR_PTR(-EINVAL); if (!kprobe_disabled(p)) { /* Disable probe if it is a child probe */ @@ -1647,8 +1652,13 @@ static struct kprobe *__disable_kprobe(struct kprobe *p) * should have already been disarmed, so * skip unneed disarming process. */ - if (!kprobes_all_disarmed) - disarm_kprobe(orig_p, true); + if (!kprobes_all_disarmed) { + ret = disarm_kprobe(orig_p, true); + if (ret) { + p->flags &= ~KPROBE_FLAG_DISABLED; + return ERR_PTR(ret); + } + } orig_p->flags |= KPROBE_FLAG_DISABLED; } } @@ -1665,8 +1675,8 @@ static int __unregister_kprobe_top(struct kprobe *p) /* Disable kprobe. This will disarm it if needed. */ ap = __disable_kprobe(p); - if (ap == NULL) - return -EINVAL; + if (IS_ERR(ap)) + return PTR_ERR(ap); if (ap == p) /* @@ -2099,12 +2109,14 @@ static void kill_kprobe(struct kprobe *p) int disable_kprobe(struct kprobe *kp) { int ret = 0; + struct kprobe *p; mutex_lock(&kprobe_mutex); /* Disable this kprobe */ - if (__disable_kprobe(kp) == NULL) - ret = -EINVAL; + p = __disable_kprobe(kp); + if (IS_ERR(p)) + ret = PTR_ERR(p); mutex_unlock(&kprobe_mutex); return ret; @@ -2474,34 +2486,48 @@ static int arm_all_kprobes(void) return ret; } -static void disarm_all_kprobes(void) +static int disarm_all_kprobes(void) { struct hlist_head *head; struct kprobe *p; - unsigned int i; + unsigned int i, errors = 0; + int err, ret = 0; mutex_lock(&kprobe_mutex); /* If kprobes are already disarmed, just return */ if (kprobes_all_disarmed) { mutex_unlock(&kprobe_mutex); - return; + return 0; } kprobes_all_disarmed = true; - printk(KERN_INFO "Kprobes globally disabled\n"); for (i = 0; i < KPROBE_TABLE_SIZE; i++) { head = &kprobe_table[i]; + /* Disarm all kprobes on a best-effort basis */ hlist_for_each_entry_rcu(p, head, hlist) { - if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p)) - disarm_kprobe(p, false); + if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p)) { + err = disarm_kprobe(p, false); + if (err) { + errors++; + ret = err; + } + } } } + + if (errors) + pr_warn("Kprobes globally disabled, but failed to disarm %d kprobes\n", errors); + else + pr_info("Kprobes globally disabled\n"); + mutex_unlock(&kprobe_mutex); /* Wait for disarming all kprobes by optimizer */ wait_for_kprobe_optimizer(); + + return ret; } /* @@ -2544,7 +2570,7 @@ static ssize_t write_enabled_file_bool(struct file *file, case 'n': case 'N': case '0': - disarm_all_kprobes(); + ret = disarm_all_kprobes(); break; default: return -EINVAL; -- 2.13.6
