firmware/efi: Add NULL pointer checks in efivars API functions

Since commit:

   ce2e6db554fa ("brcmfmac: Add support for getting nvram contents from EFI variables")

we have a device driver accessing the efivars API. Several functions in
the efivars API assume __efivars is set, i.e., that they will be accessed
only after efivars_register() has been called. However, the following NULL
pointer access was reported calling efivar_entry_size() from the brcmfmac
device driver:

  Unable to handle kernel NULL pointer dereference at virtual address 00000008
  pgd = 60bfa5f1
  [00000008] *pgd=00000000
  Internal error: Oops: 5 [#1] SMP ARM
  ...
  Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
  Workqueue: events request_firmware_work_func
  PC is at efivar_entry_size+0x28/0x90
  LR is at brcmf_fw_complete_request+0x3f8/0x8d4 [brcmfmac]
  pc : [<c0c40718>]    lr : [<bf2a3ef4>]    psr: a00d0113
  sp : ede7fe28  ip : ee983410  fp : c1787f30
  r10: 00000000  r9 : 00000000  r8 : bf2b2258
  r7 : ee983000  r6 : c1604c48  r5 : ede7fe88  r4 : edf337c0
  r3 : 00000000  r2 : 00000000  r1 : ede7fe88  r0 : c17712c8
  Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
  Control: 10c5387d  Table: ad16804a  DAC: 00000051

Disassembly showed that the local static variable __efivars is NULL,
which is not entirely unexpected given that it is a non-EFI platform.

So add a NULL pointer check to efivar_entry_size(), and to related
functions while at it. In efivars_register() a couple of sanity checks
are added as well.

Reported-by: Jon Hunter <[email protected]>
Signed-off-by: Arend van Spriel <[email protected]>
Signed-off-by: Ard Biesheuvel <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Bhupesh Sharma <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Eric Snowberg <[email protected]>
Cc: Hans de Goede <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Julien Thierry <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sai Praneeth Prakhya <[email protected]>
Cc: Sedat Dilek <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: YiFei Zhu <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions