Hi Arend,
On Tue, 13 Nov 2018 at 12:51, Arend van Spriel
<arend.vanspr...@broadcom.com> wrote:
>
> Since commit ce2e6db554fa ("brcmfmac: Add support for getting nvram
> contents from EFI variables") we have a device driver accessing the
> efivars api (since next-20181107). Several functions in efivars api
> assume __efivars is set, ie. will be accessed after efivars_register()
> has been called. However, following NULL pointer access was reported
> calling efivar_entry_size() from the brcmfmac device driver.
>
> [ 14.177769] Unable to handle kernel NULL pointer dereference at
> virtual address 00000008
> [ 14.197303] pgd = 60bfa5f1
> [ 14.211842] [00000008] *pgd=00000000
> [ 14.227373] Internal error: Oops: 5 [#1] SMP ARM
> [ 14.244244] Modules linked in: brcmfmac sha256_generic sha256_arm snd
> cfg80211 brcmutil soundcore snd_soc_tegra30_ahub tegra_wdt
> [ 14.269109] CPU: 1 PID: 114 Comm: kworker/1:2 Not tainted
> 4.20.0-rc1-next-20181107-gd881de3 #1
> [ 14.269114] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
> [ 14.269154] Workqueue: events request_firmware_work_func
> [ 14.269177] PC is at efivar_entry_size+0x28/0x90
> [ 14.269362] LR is at brcmf_fw_complete_request+0x3f8/0x8d4 [brcmfmac]
> [ 14.269369] pc : [<c0c40718>] lr : [<bf2a3ef4>] psr: a00d0113
> [ 14.269374] sp : ede7fe28 ip : ee983410 fp : c1787f30
> [ 14.269378] r10: 00000000 r9 : 00000000 r8 : bf2b2258
> [ 14.269384] r7 : ee983000 r6 : c1604c48 r5 : ede7fe88 r4 : edf337c0
> [ 14.269389] r3 : 00000000 r2 : 00000000 r1 : ede7fe88 r0 : c17712c8
> [ 14.269398] Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment
> none
> [ 14.269404] Control: 10c5387d Table: ad16804a DAC: 00000051
>
> Disassembly showed that the local static variable __efivars is NULL. Likely
> because efivars_register() is not called on this Tegra platform. So adding
> a NULL pointer check in efivar_entry_size() and similar functions while at
> it. In efivars_register() a couple of sanity checks have been added.
>
> Cc: Hans de Goede <hdego...@redhat.com>
> Reported-by: Jon Hunter <jonath...@nvidia.com>
> Signed-off-by: Arend van Spriel <arend.vanspr...@broadcom.com>
> ---
> drivers/firmware/efi/vars.c | 108
> +++++++++++++++++++++++++++++++++++---------
> 1 file changed, 87 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
> index 9336ffd..5fbd8e7 100644
> --- a/drivers/firmware/efi/vars.c
> +++ b/drivers/firmware/efi/vars.c
> @@ -318,7 +318,12 @@ struct variable_validate {
> static efi_status_t
> check_var_size(u32 attributes, unsigned long size)
> {
> - const struct efivar_operations *fops = __efivars->ops;
> + const struct efivar_operations *fops;
> +
> + if (!__efivars)
> + return EFI_UNSUPPORTED;
> +
> + fops = __efivars->ops;
>
> if (!fops->query_variable_store)
> return EFI_UNSUPPORTED;
> @@ -329,7 +334,12 @@ struct variable_validate {
> static efi_status_t
> check_var_size_nonblocking(u32 attributes, unsigned long size)
> {
> - const struct efivar_operations *fops = __efivars->ops;
> + const struct efivar_operations *fops;
> +
> + if (!__efivars)
> + return EFI_UNSUPPORTED;
> +
> + fops = __efivars->ops;
>
> if (!fops->query_variable_store)
> return EFI_UNSUPPORTED;
> @@ -429,13 +439,18 @@ static void dup_variable_bug(efi_char16_t *str16,
> efi_guid_t *vendor_guid,
> int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void
> *),
> void *data, bool duplicates, struct list_head *head)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> + const struct efivar_operations *ops;
> unsigned long variable_name_size = 1024;
> efi_char16_t *variable_name;
> efi_status_t status;
> efi_guid_t vendor_guid;
> int err = 0;
>
> + if (!__efivars)
> + return -EFAULT;
> +
> + ops = __efivars->ops;
> +
> variable_name = kzalloc(variable_name_size, GFP_KERNEL);
> if (!variable_name) {
> printk(KERN_ERR "efivars: Memory allocation failed.\n");
> @@ -583,12 +598,14 @@ static void efivar_entry_list_del_unlock(struct
> efivar_entry *entry)
> */
> int __efivar_entry_delete(struct efivar_entry *entry)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> efi_status_t status;
>
> - status = ops->set_variable(entry->var.VariableName,
> - &entry->var.VendorGuid,
> - 0, 0, NULL);
> + if (!__efivars)
> + return -EINVAL;
> +
> + status = __efivars->ops->set_variable(entry->var.VariableName,
> + &entry->var.VendorGuid,
> + 0, 0, NULL);
>
> return efi_status_to_err(status);
> }
> @@ -607,12 +624,17 @@ int __efivar_entry_delete(struct efivar_entry *entry)
> */
> int efivar_entry_delete(struct efivar_entry *entry)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> + const struct efivar_operations *ops;
> efi_status_t status;
>
> if (down_interruptible(&efivars_lock))
> return -EINTR;
>
Any reason in particular you put the check after the lock is taken? Is
this to ensure that __efivars does not change under your feet?
> + if (!__efivars) {
> + up(&efivars_lock);
> + return -EINVAL;
> + }
> + ops = __efivars->ops;
> status = ops->set_variable(entry->var.VariableName,
> &entry->var.VendorGuid,
> 0, 0, NULL);
> @@ -650,13 +672,19 @@ int efivar_entry_delete(struct efivar_entry *entry)
> int efivar_entry_set(struct efivar_entry *entry, u32 attributes,
> unsigned long size, void *data, struct list_head *head)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> + const struct efivar_operations *ops;
> efi_status_t status;
> efi_char16_t *name = entry->var.VariableName;
> efi_guid_t vendor = entry->var.VendorGuid;
>
> if (down_interruptible(&efivars_lock))
> return -EINTR;
> +
> + if (!__efivars) {
> + up(&efivars_lock);
> + return -EINVAL;
> + }
> + ops = __efivars->ops;
> if (head && efivar_entry_find(name, vendor, head, false)) {
> up(&efivars_lock);
> return -EEXIST;
> @@ -687,12 +715,17 @@ int efivar_entry_set(struct efivar_entry *entry, u32
> attributes,
> efivar_entry_set_nonblocking(efi_char16_t *name, efi_guid_t vendor,
> u32 attributes, unsigned long size, void *data)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> + const struct efivar_operations *ops;
> efi_status_t status;
>
> if (down_trylock(&efivars_lock))
> return -EBUSY;
>
> + if (!__efivars) {
> + up(&efivars_lock);
> + return -EINVAL;
> + }
> +
> status = check_var_size_nonblocking(attributes,
> size + ucs2_strsize(name, 1024));
> if (status != EFI_SUCCESS) {
> @@ -700,6 +733,7 @@ int efivar_entry_set(struct efivar_entry *entry, u32
> attributes,
> return -ENOSPC;
> }
>
> + ops = __efivars->ops;
> status = ops->set_variable_nonblocking(name, &vendor, attributes,
> size, data);
>
> @@ -727,9 +761,13 @@ int efivar_entry_set(struct efivar_entry *entry, u32
> attributes,
> int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32
> attributes,
> bool block, unsigned long size, void *data)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> + const struct efivar_operations *ops;
> efi_status_t status;
>
> + if (!__efivars)
> + return -EINVAL;
> +
> + ops = __efivars->ops;
> if (!ops->query_variable_store)
> return -ENOSYS;
>
> @@ -829,13 +867,18 @@ struct efivar_entry *efivar_entry_find(efi_char16_t
> *name, efi_guid_t guid,
> */
> int efivar_entry_size(struct efivar_entry *entry, unsigned long *size)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> + const struct efivar_operations *ops;
> efi_status_t status;
>
> *size = 0;
>
> if (down_interruptible(&efivars_lock))
> return -EINTR;
> + if (!__efivars) {
> + up(&efivars_lock);
> + return -EINVAL;
> + }
> + ops = __efivars->ops;
> status = ops->get_variable(entry->var.VariableName,
> &entry->var.VendorGuid, NULL, size, NULL);
> up(&efivars_lock);
> @@ -861,12 +904,14 @@ int efivar_entry_size(struct efivar_entry *entry,
> unsigned long *size)
> int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
> unsigned long *size, void *data)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> efi_status_t status;
>
> - status = ops->get_variable(entry->var.VariableName,
> - &entry->var.VendorGuid,
> - attributes, size, data);
> + if (!__efivars)
> + return -EINVAL;
> +
> + status = __efivars->ops->get_variable(entry->var.VariableName,
> + &entry->var.VendorGuid,
> + attributes, size, data);
>
> return efi_status_to_err(status);
> }
> @@ -882,14 +927,19 @@ int __efivar_entry_get(struct efivar_entry *entry, u32
> *attributes,
> int efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
> unsigned long *size, void *data)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> efi_status_t status;
>
> if (down_interruptible(&efivars_lock))
> return -EINTR;
> - status = ops->get_variable(entry->var.VariableName,
> - &entry->var.VendorGuid,
> - attributes, size, data);
> +
> + if (!__efivars) {
> + up(&efivars_lock);
> + return -EINVAL;
> + }
> +
> + status = __efivars->ops->get_variable(entry->var.VariableName,
> + &entry->var.VendorGuid,
> + attributes, size, data);
> up(&efivars_lock);
>
> return efi_status_to_err(status);
> @@ -921,7 +971,7 @@ int efivar_entry_get(struct efivar_entry *entry, u32
> *attributes,
> int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
> unsigned long *size, void *data, bool *set)
> {
> - const struct efivar_operations *ops = __efivars->ops;
> + const struct efivar_operations *ops;
> efi_char16_t *name = entry->var.VariableName;
> efi_guid_t *vendor = &entry->var.VendorGuid;
> efi_status_t status;
> @@ -940,6 +990,11 @@ int efivar_entry_set_get_size(struct efivar_entry
> *entry, u32 attributes,
> if (down_interruptible(&efivars_lock))
> return -EINTR;
>
> + if (!__efivars) {
> + err = -EINVAL;
> + goto out;
> + }
> +
> /*
> * Ensure that the available space hasn't shrunk below the safe level
> */
> @@ -956,6 +1011,8 @@ int efivar_entry_set_get_size(struct efivar_entry
> *entry, u32 attributes,
> }
> }
>
> + ops = __efivars->ops;
> +
> status = ops->set_variable(name, vendor, attributes, *size, data);
> if (status != EFI_SUCCESS) {
> err = efi_status_to_err(status);
> @@ -1138,6 +1195,15 @@ int efivars_register(struct efivars *efivars,
> if (down_interruptible(&efivars_lock))
> return -EINTR;
>
> + if (WARN(!efivars || !ops, "Invalid parameters\n"))
> + return -EINVAL;
> +
> + /* check mandatory efivars operations */
> + if (WARN_ON(!ops->get_variable) ||
> + WARN_ON(!ops->set_variable) ||
> + WARN_ON(!ops->get_next_variable))
> + return -EINVAL;
> +
> efivars->ops = ops;
> efivars->kobject = kobject;
>
> --
> 1.9.1
>
