Commit-ID: 705feaf321c37e4dca3637fd5cb3b275f17a06c9
Gitweb: https://git.kernel.org/tip/705feaf321c37e4dca3637fd5cb3b275f17a06c9
Author: Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Mon, 12 Mar 2018 14:45:45 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 13 Mar 2018 06:56:08 +0100
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@xxxxxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx>
Cc: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Milind Chabbi <chabbi.milind@xxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Oleg Nesterov <onestero@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Link: http://lkml.kernel.org/r/20180312134548.31532-6-jolsa@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/events/hw_breakpoint.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index a556aba223da..0c82663395f7 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -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)
--
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