The patch titled
Subject: kprobes: use strncpy_from_kernel_nofault() in fetch_store_string()
has been added to the -mm tree. Its filename is
tracing-kprobes-handle-mixed-kernel-userspace-probes-better-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/tracing-kprobes-handle-mixed-kernel-userspace-probes-better-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/tracing-kprobes-handle-mixed-kernel-userspace-probes-better-fix.patch
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------------------------------------------------------
From: Sven Schnelle <svens@xxxxxxxxxxxxx>
Subject: kprobes: use strncpy_from_kernel_nofault() in fetch_store_string()
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 >events/kprobes/testprobe/enable
cat trace
it will just show
test.sh-519 [012] .... 18.580625: testprobe: (_do_fork+0x0/0x3c8) comm=(fault)
Looking at the source 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
fetch_store_string() should use strncpy_from_kernel_nofault().
Link: http://lkml.kernel.org/r/20200606181903.49384-1-svens@xxxxxxxxxxxxx
Signed-off-by: Sven Schnelle <svens@xxxxxxxxxxxxx>
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Acked-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace_kprobe.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/trace/trace_kprobe.c~tracing-kprobes-handle-mixed-kernel-userspace-probes-better-fix
+++ a/kernel/trace/trace_kprobe.c
@@ -1278,7 +1278,7 @@ fetch_store_string(unsigned long addr, v
* Try to get string again, since the string can be changed while
* probing.
*/
- ret = strncpy_from_user_nofault(__dest, (void *)addr, maxlen);
+ ret = strncpy_from_kernel_nofault(__dest, (void *)addr, maxlen);
if (ret >= 0)
*(u32 *)dest = make_data_loc(ret, __dest - base);
_
Patches currently in -mm which might be from svens@xxxxxxxxxxxxx are
tracing-kprobes-handle-mixed-kernel-userspace-probes-better-fix.patch
