[Coverity CID :208191] Dereference after null check in subsys/canbus/isotp/isotp.c

[zephyrbot]

Static code scan issues found in file:

https://github.com/zephyrproject-rtos/zephyr/tree/e089906b339aad4cd1b6589a3b6ce94782d93f54/subsys/canbus/isotp/isotp.c#L437

Category: Null pointer dereferences
Function: receive_add_mem
Component: Other
CID: 208191

Details:

431         ctx->act_frag = ctx->act_frag->frags;
432         if (!ctx->act_frag) {
433             LOG_ERR("No fragmet left to append data");
434             receive_report_error(ctx, ISOTP_N_BUFFER_OVERFLW);
435         }
436    
>>>     CID 208191:  Null pointer dereferences  (FORWARD_NULL)
>>>     Passing null pointer "&(*ctx->act_frag).b" to "net_buf_simple_add_mem", which dereferences it.
437         net_buf_add_mem(ctx->act_frag, data + tailroom, len - tailroom);
438     }
439    
440     static void process_cf(struct isotp_recv_ctx *ctx, struct zcan_frame *frame)
441     {
442         u32_t *ud_rem_len = (u32_t *)net_buf_user_data(ctx->buf);

Please fix or provide comments in coverity using the link:

https://scan9.coverity.com/reports.htm#v32951/p12996.

Note: This issue was created automatically. Priority was set based on classification
of the file affected and the impact field in coverity. Assignees were set using the CODEOWNERS file.