[PATCH 12/23] bpf: handle the compat string in bpf_trace_copy_string better

[Christoph Hellwig]

User the proper helper for kernel or userspace addresses based on
TASK_SIZE instead of the dangerous strncpy_from_unsafe function.

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 kernel/trace/bpf_trace.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 9d4080590f711..737d739230a6b 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -331,8 +331,11 @@ static void bpf_trace_copy_string(char *buf, void 
*unsafe_ptr, char fmt_ptype,
        switch (fmt_ptype) {
        case 's':
 #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
-               strncpy_from_unsafe(buf, unsafe_ptr, bufsz);
-               break;
+               if ((unsigned long)unsafe_ptr < TASK_SIZE) {
+                       strncpy_from_user_nofault(buf, user_ptr, bufsz);
+                       break;
+               }
+               fallthrough;
 #endif
        case 'k':
                strncpy_from_kernel_nofault(buf, unsafe_ptr, bufsz);
-- 
2.26.2