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soc: aspeed: lpc-snoop: Don't disable channels that aren't enabled
Mitigate e.g. the following: # echo 1e789080.lpc-snoop > /sys/bus/platform/drivers/aspeed-lpc-snoop/unbind ... [ 120.363594] Unable to handle kernel NULL pointer dereference at virtual address 00000004 when write [ 120.373866] [00000004] *pgd=00000000 [ 120.377910] Internal error: Oops: 805 [kernel-patches#1] SMP ARM [ 120.383306] CPU: 1 UID: 0 PID: 315 Comm: sh Not tainted 6.15.0-rc1-00009-g926217bc7d7d-dirty kernel-patches#20 NONE ... [ 120.679543] Call trace: [ 120.679559] misc_deregister from aspeed_lpc_snoop_remove+0x84/0xac [ 120.692462] aspeed_lpc_snoop_remove from platform_remove+0x28/0x38 [ 120.700996] platform_remove from device_release_driver_internal+0x188/0x200 ... Fixes: 9f4f9ae ("drivers/misc: add Aspeed LPC snoop driver") Cc: [email protected] Cc: Jean Delvare <[email protected]> Acked-by: Jean Delvare <[email protected]> Link: https://patch.msgid.link/20250616-aspeed-lpc-snoop-fixes-v2-2-3cdd59c934d3@codeconstruct.com.au Signed-off-by: Andrew Jeffery <[email protected]>
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drivers/soc/aspeed/aspeed-lpc-snoop.c

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -58,6 +58,7 @@ struct aspeed_lpc_snoop_model_data {
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};
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struct aspeed_lpc_snoop_channel {
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bool enabled;
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struct kfifo fifo;
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wait_queue_head_t wq;
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struct miscdevice miscdev;
@@ -190,6 +191,9 @@ static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
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const struct aspeed_lpc_snoop_model_data *model_data =
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of_device_get_match_data(dev);
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if (WARN_ON(lpc_snoop->chan[channel].enabled))
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return -EBUSY;
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init_waitqueue_head(&lpc_snoop->chan[channel].wq);
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/* Create FIFO datastructure */
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rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
@@ -236,6 +240,8 @@ static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
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regmap_update_bits(lpc_snoop->regmap, HICRB,
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hicrb_en, hicrb_en);
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lpc_snoop->chan[channel].enabled = true;
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return 0;
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err_misc_deregister:
@@ -248,6 +254,9 @@ static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
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static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
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int channel)
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{
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if (!lpc_snoop->chan[channel].enabled)
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return;
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switch (channel) {
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case 0:
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regmap_update_bits(lpc_snoop->regmap, HICR5,
@@ -263,6 +272,8 @@ static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
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return;
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}
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lpc_snoop->chan[channel].enabled = false;
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/* Consider improving safety wrt concurrent reader(s) */
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misc_deregister(&lpc_snoop->chan[channel].miscdev);
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kfifo_free(&lpc_snoop->chan[channel].fifo);
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}

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