[PATCH net-next v5 7/8] net: pktgen: fix access outside of user given buffer in pktgen_thread_write()

[Peter Seiderer]

Honour the user given buffer size for the strn_len() calls (otherwise
strn_len() will access memory outside of the user given buffer).

Signed-off-by: Peter Seiderer <ps.rep...@gmx.net>
Reviewed-by: Simon Horman <ho...@kernel.org>
---
Changes v4 -> v5
  - split up patchset into part i/ii (suggested by Simon Horman)

Changes v3 -> v4
  - add rev-by Simon Horman

Changes v2 -> v3:
  - no changes

Changes v1 -> v2:
  - no changes
---
 net/core/pktgen.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index f6e35ba035c7..55064713223e 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -1900,8 +1900,8 @@ static ssize_t pktgen_thread_write(struct file *file,
        i = len;
 
        /* Read variable name */
-
-       len = strn_len(&user_buffer[i], sizeof(name) - 1);
+       max = min(sizeof(name) - 1, count - i);
+       len = strn_len(&user_buffer[i], max);
        if (len < 0)
                return len;
 
@@ -1931,7 +1931,8 @@ static ssize_t pktgen_thread_write(struct file *file,
        if (!strcmp(name, "add_device")) {
                char f[32];
                memset(f, 0, 32);
-               len = strn_len(&user_buffer[i], sizeof(f) - 1);
+               max = min(sizeof(f) - 1, count - i);
+               len = strn_len(&user_buffer[i], max);
                if (len < 0) {
                        ret = len;
                        goto out;
-- 
2.48.1