wifi: brcmfmac: pcie: handle randbuf allocation failure

The kzalloc() in brcmf_pcie_download_fw_nvram() will return null
if the physical memory has run out. As a result, if we use
get_random_bytes() to generate random bytes in the randbuf, the
null pointer dereference bug will happen.

In order to prevent allocation failure, this patch adds a separate
function using buffer on kernel stack to generate random bytes in
the randbuf, which could prevent the kernel stack from overflow.

Fixes: 91918ce88d9f ("wifi: brcmfmac: pcie: Provide a buffer of random bytes to the device")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240306140437.18177-1-duoming@zju.edu.cn

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
index d7fb88bb6ae1a3ff9975966f727810abda27ae1a..06698a714b5233485ad9f45af41db0583c6d92d8 100644 (file)
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
@@ -1675,6 +1675,15 @@ struct brcmf_random_seed_footer {
 #define BRCMF_RANDOM_SEED_MAGIC                0xfeedc0de
 #define BRCMF_RANDOM_SEED_LENGTH       0x100
 
+static noinline_for_stack void
+brcmf_pcie_provide_random_bytes(struct brcmf_pciedev_info *devinfo, u32 address)
+{
+       u8 randbuf[BRCMF_RANDOM_SEED_LENGTH];
+
+       get_random_bytes(randbuf, BRCMF_RANDOM_SEED_LENGTH);
+       memcpy_toio(devinfo->tcm + address, randbuf, BRCMF_RANDOM_SEED_LENGTH);
+}
+
 static int brcmf_pcie_download_fw_nvram(struct brcmf_pciedev_info *devinfo,
                                        const struct firmware *fw, void *nvram,
                                        u32 nvram_len)
@@ -1717,7 +1726,6 @@ static int brcmf_pcie_download_fw_nvram(struct brcmf_pciedev_info *devinfo,
                                .length = cpu_to_le32(rand_len),
                                .magic = cpu_to_le32(BRCMF_RANDOM_SEED_MAGIC),
                        };
-                       void *randbuf;
 
                        /* Some Apple chips/firmwares expect a buffer of random
                         * data to be present before NVRAM
@@ -1729,10 +1737,7 @@ static int brcmf_pcie_download_fw_nvram(struct brcmf_pciedev_info *devinfo,
                                    sizeof(footer));
 
                        address -= rand_len;
-                       randbuf = kzalloc(rand_len, GFP_KERNEL);
-                       get_random_bytes(randbuf, rand_len);
-                       memcpy_toio(devinfo->tcm + address, randbuf, rand_len);
-                       kfree(randbuf);
+                       brcmf_pcie_provide_random_bytes(devinfo, address);
                }
        } else {
                brcmf_dbg(PCIE, "No matching NVRAM file found %s\n",