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Subject[PATCH bpf-next v3 3/4] bpf_trace: handle compat in copy_user_syms
For compat processes, userspace size for syms pointers is different.
Provide compat handling for copying array elements from the user space.

Fixes: 0dcac272540613d4 ("bpf: Add multi kprobe link")
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
---
kernel/trace/bpf_trace.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index a93a54f..9d3028a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2253,6 +2253,24 @@ struct user_syms {
char *buf;
};

+static inline int get_arr_ptr(unsigned long *p,
+ unsigned long __user *uaddr, u32 idx)
+{
+ if (unlikely(in_compat_syscall())) {
+ compat_uptr_t __user *compat_uaddr = (compat_uptr_t __user *)uaddr;
+ compat_uptr_t val;
+ int err;
+
+ err = __get_user(val, compat_uaddr + idx);
+ if (!err)
+ *p = val;
+
+ return err;
+ } else {
+ return __get_user(*p, uaddr + idx);
+ }
+}
+
static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt)
{
unsigned long __user usymbol;
@@ -2270,7 +2288,7 @@ static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32
goto error;

for (p = buf, i = 0; i < cnt; i++) {
- if (__get_user(usymbol, usyms + i)) {
+ if (get_arr_ptr(&usymbol, usyms, i)) {
err = -EFAULT;
goto error;
}
--
2.1.4
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