wifi: mt76: mt7921: fix error code of return in mt7921_acpi_read

[ Upstream commit 888d89034f9eaeab9b5b75f13dbe35376c7dd471 ]

Kernel NULL pointer dereference when ACPI SAR table isn't implemented well.
Fix the error code of return to mark the ACPI SAR table as invalid.

[    5.077128] mt7921e 0000:06:00.0: sar cnt = 0
[    5.077381] BUG: kernel NULL pointer dereference, address:
0000000000000004
[    5.077630] #PF: supervisor read access in kernel mode
[    5.077883] #PF: error_code(0x0000) - not-present page
[    5.078138] PGD 0 P4D 0
[    5.078398] Oops: 0000 [#1] PREEMPT SMP NOPTI
[    5.079202] RIP: 0010:mt7921_init_acpi_sar+0x106/0x220
[mt7921_common]
...
[    5.080786] Call Trace:
[    5.080786]  <TASK>
[    5.080786]  mt7921_register_device+0x37d/0x490 [mt7921_common]
[    5.080786]  mt7921_pci_probe.part.0+0x2ee/0x310 [mt7921e]
[    5.080786]  mt7921_pci_probe+0x52/0x70 [mt7921e]
[    5.080786]  local_pci_probe+0x47/0x90
[    5.080786]  pci_call_probe+0x55/0x190
[    5.080786]  pci_device_probe+0x84/0x120

Fixes: f965333e491e ("mt76: mt7921: introduce ACPI SAR support")
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/acpi_sar.c b/drivers/net/wireless/mediatek/mt76/mt7921/acpi_sar.c
index 47e034a..ed9241d 100644 (file)
--- a/drivers/net/wireless/mediatek/mt76/mt7921/acpi_sar.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/acpi_sar.c
@@ -33,14 +33,17 @@ mt7921_acpi_read(struct mt7921_dev *dev, u8 *method, u8 **tbl, u32 *len)
            sar_root->package.elements[0].type != ACPI_TYPE_INTEGER) {
                dev_err(mdev->dev, "sar cnt = %d\n",
                        sar_root->package.count);
+               ret = -EINVAL;
                goto free;
        }
 
        if (!*tbl) {
                *tbl = devm_kzalloc(mdev->dev, sar_root->package.count,
                                    GFP_KERNEL);
-               if (!*tbl)
+               if (!*tbl) {
+                       ret = -ENOMEM;
                        goto free;
+               }
        }
        if (len)
                *len = sar_root->package.count;
@@ -52,9 +55,9 @@ mt7921_acpi_read(struct mt7921_dev *dev, u8 *method, u8 **tbl, u32 *len)
                        break;
                *(*tbl + i) = (u8)sar_unit->integer.value;
        }
-free:
        ret = (i == sar_root->package.count) ? 0 : -EINVAL;
 
+free:
        kfree(sar_root);
 
        return ret;