Messages in this thread | | | Date | Fri, 5 Jun 2020 19:44:33 +0200 | From | Sven Schnelle <> | Subject | Re: kprobes string reading broken on s390 |
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Masami,
On Sat, Jun 06, 2020 at 01:58:06AM +0900, Masami Hiramatsu wrote: > Hi Sven, > > On Fri, 5 Jun 2020 15:25:41 +0200 > Christoph Hellwig <hch@lst.de> wrote: > > > Yes, this looks correct. You probably want to write a small changelog > > and add a Fixes tag, though. > > > > On Fri, Jun 05, 2020 at 01:05:34PM +0200, Sven Schnelle wrote: > > > Hi Christoph, > > > > > > with the latest linux-next i noticed that some tests in the > > > ftrace test suites are failing on s390, namely: > > > > > > [FAIL] Kprobe event symbol argument > > > [FAIL] Kprobe event with comm arguments > > > > > > The following doesn't work anymore: > > > > > > cd /sys/kernel/tracing > > > echo 'p:testprobe _do_fork comm=$comm ' >kprobe_events > > > echo 1 >/sys/kernel/tracing/events/kprobes/testprobe/enable > > > cat /sys/kernel/tracing/trace > > > > > > it will just show > > > > > > test.sh-519 [012] .... 18.580625: testprobe: (_do_fork+0x0/0x3c8) comm=(fault) > > > > > > Looking at d411a9c4e95a ("tracing/kprobes: handle mixed kernel/userspace probes > > > better") i see that there are two helpers for reading strings: > > > > > > fetch_store_string_user() -> read string from user space > > > fetch_store_string() -> read string from kernel space(?) > > > > > > but in the end both are using strncpy_from_user_nofault(), but i would > > > think that fetch_store_string() should use strncpy_from_kernel_nofault(). > > > However, i'm not sure about the exact semantics of fetch_store_string(), > > > as there where a lot of wrong assumptions in the past, especially since > > > on x86 you usually don't fail if you use the same function for accessing kernel > > > and userspace although it's technically wrong. > > Thanks for fixing! > This report can be a good changelog. > Please resend it with Fixed tag as Christoph said.
Which SHA1 should the Fixes tag carry? The one from linux-next?
Regards Sven
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