lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 27 Aug 2020 20:37:38 +0900 From: Masami Hiramatsu <mhiramat@...nel.org> To: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org> Cc: Eddy Wu <Eddy_Wu@...ndmicro.com>, x86@...nel.org, "David S . Miller" <davem@...emloft.net>, Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...hat.com>, "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>, Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>, linux-arch@...r.kernel.org Subject: [PATCH v2 14/15] kprobes: Remove NMI context check Since the commit 9b38cc704e84 ("kretprobe: Prevent triggering kretprobe from within kprobe_flush_task") sets a dummy current kprobe in the trampoline handler by kprobe_busy_begin/end(), it is not possible to run a kretprobe pre handler in kretprobe trampoline handler context even with the NMI. If the NMI interrupts a kretprobe_trampoline_handler() and it hits a kretprobe, the 2nd kretprobe will detect recursion correctly and it will be skipped. This means we have almost no double-lock issue on kretprobes by NMI. The last one point is in cleanup_rp_inst() which also takes kretprobe_table_lock without setting up current kprobes. So adding kprobe_busy_begin/end() there allows us to remove in_nmi() check. The above commit applies kprobe_busy_begin/end() on x86, but now all arch implementation are unified to generic one, we can safely remove the in_nmi() check from arch independent code. Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org> --- kernel/kprobes.c | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index cbd2ad1af7b7..311033e4b8e4 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); @@ -2038,17 +2041,6 @@ 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);
Powered by blists - more mailing lists