mISDN: Update parameter type of dsp_cmx_send()

When booting a kernel with CONFIG_MISDN_DSP=y and CONFIG_CFI_CLANG=y,
there is a failure when dsp_cmx_send() is called indirectly from
call_timer_fn():

  [    0.371412] CFI failure at call_timer_fn+0x2f/0x150 (target: dsp_cmx_send+0x0/0x530; expected type: 0x92ada1e9)

The function pointer prototype that call_timer_fn() expects is

  void (*fn)(struct timer_list *)

whereas dsp_cmx_send() has a parameter type of 'void *', which causes
the control flow integrity checks to fail because the parameter types do
not match.

Change dsp_cmx_send()'s parameter type to be 'struct timer_list' to
match the expected prototype. The argument is unused anyways, so this
has no functional change, aside from avoiding the CFI failure.
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202308020936.58787e6c-oliver.sang@intel.comSigned-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Fixes: e313ac12 ("mISDN: Convert timers to use timer_setup()")
Link: https://lore.kernel.org/r/20230802-fix-dsp_cmx_send-cfi-failure-v1-1-2f2e79b0178d@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/isdn/mISDN/dsp.h

@@ -247,7 +247,7 @@ extern void dsp_cmx_hardware(struct dsp_conf *conf, struct dsp *dsp);
 extern int dsp_cmx_conf(struct dsp *dsp, u32 conf_id);
 extern void dsp_cmx_receive(struct dsp *dsp, struct sk_buff *skb);
 extern void dsp_cmx_hdlc(struct dsp *dsp, struct sk_buff *skb);
-extern void dsp_cmx_send(void *arg);
+extern void dsp_cmx_send(struct timer_list *arg);
 extern void dsp_cmx_transmit(struct dsp *dsp, struct sk_buff *skb);
 extern int dsp_cmx_del_conf_member(struct dsp *dsp);
 extern int dsp_cmx_del_conf(struct dsp_conf *conf);

drivers/isdn/mISDN/dsp_cmx.c

@@ -1614,7 +1614,7 @@ static u16	dsp_count; /* last sample count */
 static int	dsp_count_valid; /* if we have last sample count */
 
 void
-dsp_cmx_send(void *arg)
+dsp_cmx_send(struct timer_list *arg)
 {
 	struct dsp_conf *conf;
 	struct dsp_conf_member *member;

drivers/isdn/mISDN/dsp_core.c

@@ -1195,7 +1195,7 @@ static int __init dsp_init(void)
 	}
 
 	/* set sample timer */
-	timer_setup(&dsp_spl_tl, (void *)dsp_cmx_send, 0);
+	timer_setup(&dsp_spl_tl, dsp_cmx_send, 0);
 	dsp_spl_tl.expires = jiffies + dsp_tics;
 	dsp_spl_jiffies = dsp_spl_tl.expires;
 	add_timer(&dsp_spl_tl);