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| author |   Masami Hiramatsu <mhiramat@kernel.org> | 2020-08-29 22:02:36 +0900 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2020-09-08 11:52:35 +0200 |
| commit | e03b4a084ea6b0a18b0e874baec439e69090c168 (patch) | |
| tree | 7648ae43bbe8a8f8ea2f1cd716043d1a1f04bb6a /kernel/kprobes.c | |
| parent | sparc: kprobes: Use generic kretprobe trampoline handler (diff) | |
| download | linux-dev-e03b4a084ea6b0a18b0e874baec439e69090c168.tar.xz linux-dev-e03b4a084ea6b0a18b0e874baec439e69090c168.zip | |
kprobes: Remove NMI context check
The in_nmi() check in pre_handler_kretprobe() is meant to avoid
recursion, and blindly assumes that anything NMI is recursive.
However, since commit:
9b38cc704e84 ("kretprobe: Prevent triggering kretprobe from within kprobe_flush_task")
there is a better way to detect and avoid actual recursion.
By setting a dummy kprobe, any actual exceptions will terminate early
(by trying to handle the dummy kprobe), and recursion will not happen.
Employ this to avoid the kretprobe_table_lock() recursion, replacing
the over-eager in_nmi() check.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/159870615628.1229682.6087311596892125907.stgit@devnote2
Diffstat (limited to 'kernel/kprobes.c')
| -rw-r--r-- | kernel/kprobes.c | 16 |
1 files changed, 4 insertions, 12 deletions
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index a0afaa79024e..211138225fa5 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1359,7 +1359,8 @@ static void cleanup_rp_inst(struct kretprobe *rp) struct hlist_node *next; struct hlist_head *head; - /* No race here */ + /* To avoid recursive kretprobe by NMI, set kprobe busy here */ + kprobe_busy_begin(); for (hash = 0; hash < KPROBE_TABLE_SIZE; hash++) { kretprobe_table_lock(hash, &flags); head = &kretprobe_inst_table[hash]; @@ -1369,6 +1370,8 @@ static void cleanup_rp_inst(struct kretprobe *rp) } kretprobe_table_unlock(hash, &flags); } + kprobe_busy_end(); + free_rp_inst(rp); } NOKPROBE_SYMBOL(cleanup_rp_inst); @@ -2035,17 +2038,6 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) unsigned long hash, flags = 0; struct kretprobe_instance *ri; - /* - * To avoid deadlocks, prohibit return probing in NMI contexts, - * just skip the probe and increase the (inexact) 'nmissed' - * statistical counter, so that the user is informed that - * something happened: - */ - if (unlikely(in_nmi())) { - rp->nmissed++; - return 0; - } - /* TODO: consider to only swap the RA after the last pre_handler fired */ hash = hash_ptr(current, KPROBE_HASH_BITS); raw_spin_lock_irqsave(&rp->lock, flags); |