ASoC: meson: axg-card: fix 'use-after-free'

commit 4f9a714 upstream.

Buffer 'card->dai_link' is reallocated in 'meson_card_reallocate_links()',
so move 'pad' pointer initialization after this function when memory is
already reallocated.

Kasan bug report:

==================================================================
BUG: KASAN: slab-use-after-free in axg_card_add_link+0x76c/0x9bc
Read of size 8 at addr ffff000000e8b260 by task modprobe/356

CPU: 0 PID: 356 Comm: modprobe Tainted: G O 6.9.12-sdkernel #1
Call trace:
 dump_backtrace+0x94/0xec
 show_stack+0x18/0x24
 dump_stack_lvl+0x78/0x90
 print_report+0xfc/0x5c0
 kasan_report+0xb8/0xfc
 __asan_load8+0x9c/0xb8
 axg_card_add_link+0x76c/0x9bc [snd_soc_meson_axg_sound_card]
 meson_card_probe+0x344/0x3b8 [snd_soc_meson_card_utils]
 platform_probe+0x8c/0xf4
 really_probe+0x110/0x39c
 __driver_probe_device+0xb8/0x18c
 driver_probe_device+0x108/0x1d8
 __driver_attach+0xd0/0x25c
 bus_for_each_dev+0xe0/0x154
 driver_attach+0x34/0x44
 bus_add_driver+0x134/0x294
 driver_register+0xa8/0x1e8
 __platform_driver_register+0x44/0x54
 axg_card_pdrv_init+0x20/0x1000 [snd_soc_meson_axg_sound_card]
 do_one_initcall+0xdc/0x25c
 do_init_module+0x10c/0x334
 load_module+0x24c4/0x26cc
 init_module_from_file+0xd4/0x128
 __arm64_sys_finit_module+0x1f4/0x41c
 invoke_syscall+0x60/0x188
 el0_svc_common.constprop.0+0x78/0x13c
 do_el0_svc+0x30/0x40
 el0_svc+0x38/0x78
 el0t_64_sync_handler+0x100/0x12c
 el0t_64_sync+0x190/0x194

Fixes: 7864a79 ("ASoC: meson: add axg sound card support")
Cc: [email protected]
Signed-off-by: Arseniy Krasnov <[email protected]>
Reviewed-by: Jerome Brunet <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Arseniy Krasnov

sound/soc/meson/axg-card.c

@@ -104,7 +104,7 @@ static int axg_card_add_tdm_loopback(struct snd_soc_card *card,
 				     int *index)
 {
 	struct meson_card *priv = snd_soc_card_get_drvdata(card);
-	struct snd_soc_dai_link *pad = &card->dai_link[*index];
+	struct snd_soc_dai_link *pad;
 	struct snd_soc_dai_link *lb;
 	struct snd_soc_dai_link_component *dlc;
 	int ret;
@@ -114,6 +114,7 @@ static int axg_card_add_tdm_loopback(struct snd_soc_card *card,
 	if (ret)
 		return ret;
 
+	pad = &card->dai_link[*index];
 	lb = &card->dai_link[*index + 1];
 
 	lb->name = devm_kasprintf(card->dev, GFP_KERNEL, "%s-lb", pad->name);