• Ricardo Neri's avatar
    efi: Check for NULL efi kernel parameters · 9115c758
    Ricardo Neri authored
    Even though it is documented how to specifiy efi parameters, it is
    possible to cause a kernel panic due to a dereference of a NULL pointer when
    parsing such parameters if "efi" alone is given:
    
    PANIC: early exception 0e rip 10:ffffffff812fb361 error 0 cr2 0
    [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.2.0-rc1+ #450
    [ 0.000000]  ffffffff81fe20a9 ffffffff81e03d50 ffffffff8184bb0f 00000000000003f8
    [ 0.000000]  0000000000000000 ffffffff81e03e08 ffffffff81f371a1 64656c62616e6520
    [ 0.000000]  0000000000000069 000000000000005f 0000000000000000 0000000000000000
    [ 0.000000] Call Trace:
    [ 0.000000]  [<ffffffff8184bb0f>] dump_stack+0x45/0x57
    [ 0.000000]  [<ffffffff81f371a1>] early_idt_handler_common+0x81/0xae
    [ 0.000000]  [<ffffffff812fb361>] ? parse_option_str+0x11/0x90
    [ 0.000000]  [<ffffffff81f4dd69>] arch_parse_efi_cmdline+0x15/0x42
    [ 0.000000]  [<ffffffff81f376e1>] do_early_param+0x50/0x8a
    [ 0.000000]  [<ffffffff8106b1b3>] parse_args+0x1e3/0x400
    [ 0.000000]  [<ffffffff81f37a43>] parse_early_options+0x24/0x28
    [ 0.000000]  [<ffffffff81f37691>] ? loglevel+0x31/0x31
    [ 0.000000]  [<ffffffff81f37a78>] parse_early_param+0x31/0x3d
    [ 0.000000]  [<ffffffff81f3ae98>] setup_arch+0x2de/0xc08
    [ 0.000000]  [<ffffffff8109629a>] ? vprintk_default+0x1a/0x20
    [ 0.000000]  [<ffffffff81f37b20>] start_kernel+0x90/0x423
    [ 0.000000]  [<ffffffff81f37495>] x86_64_start_reservations+0x2a/0x2c
    [ 0.000000]  [<ffffffff81f37582>] x86_64_start_kernel+0xeb/0xef
    [ 0.000000] RIP 0xffffffff81ba2efc
    
    This panic is not reproducible with "efi=" as this will result in a non-NULL
    zero-length string.
    
    Thus, verify that the pointer to the parameter string is not NULL. This is
    consistent with other parameter-parsing functions which check for NULL pointers.
    Signed-off-by: default avatarRicardo Neri <ricardo.neri-calderon@linux.intel.com>
    Cc: Dave Young <dyoung@redhat.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
    9115c758
efi.c 24.3 KB