Commit 705feaf3 authored Mar 12, 2018 by Jiri Olsa Committed by Ingo Molnar Mar 13, 2018

hw_breakpoint: Add perf_event_attr fields check in __modify_user_hw_breakpoint()



And rename it to modify_user_hw_breakpoint_check().

We are about to use modify_user_hw_breakpoint_check() for user space
breakpoints modification, we must be very strict to check only the
fields we can change have changed. As Peter explained:

 "Suppose someone does:

        attr = malloc(sizeof(*attr)); // uninitialized memory
        attr->type = BP;
        attr->bp_addr = new_addr;
        attr->bp_type = bp_type;
        attr->bp_len = bp_len;
        ioctl(fd, PERF_IOC_MOD_ATTR, &attr);

  And feeds absolute shite for the rest of the fields.
  Then we later want to extend IOC_MOD_ATTR to allow changing
  attr::sample_type but we can't, because that would break the
  above application."

I'm making this check optional because we already export
modify_user_hw_breakpoint() and with this check we could
break existing users.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20180312134548.31532-6-jolsa@kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 18ff57b2

kernel/events/hw_breakpoint.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -456,7 +456,9 @@ register_user_hw_breakpoint(struct perf_event_attr *attr,
		}
		EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);

		static int __modify_user_hw_breakpoint(struct perf_event bp, struct perf_event_attr attr)
		static int
		modify_user_hw_breakpoint_check(struct perf_event bp, struct perf_event_attr attr,
		bool check)
		{
		u64 old_addr = bp->attr.bp_addr;
		u64 old_len = bp->attr.bp_len;
		@@ -468,6 +470,9 @@ static int __modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_
		bp->attr.bp_type = attr->bp_type;
		bp->attr.bp_len = attr->bp_len;

		if (check && memcmp(&bp->attr, attr, sizeof(*attr)))
		return -EINVAL;

		err = validate_hw_breakpoint(bp);
		if (!err && modify)
		err = modify_bp_slot(bp, old_type);
		@@ -505,7 +510,7 @@ int modify_user_hw_breakpoint(struct perf_event bp, struct perf_event_attr att
		else
		perf_event_disable(bp);

		err = __modify_user_hw_breakpoint(bp, attr);
		err = modify_user_hw_breakpoint_check(bp, attr, false);

		if (err) {
		if (!bp->attr.disabled)