lkml.org 
[lkml]   [2019]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH AUTOSEL 4.19 01/52] ARC: u-boot args: check that magic number is correct
    Date
    From: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>

    [ Upstream commit edb64bca50cd736c6894cc6081d5263c007ce005 ]

    In case of devboards we really often disable bootloader and load
    Linux image in memory via JTAG. Even if kernel tries to verify
    uboot_tag and uboot_arg there is sill a chance that we treat some
    garbage in registers as valid u-boot arguments in JTAG case.
    E.g. it is enough to have '1' in r0 to treat any value in r2 as
    a boot command line.

    So check that magic number passed from u-boot is correct and drop
    u-boot arguments otherwise. That helps to reduce the possibility
    of using garbage as u-boot arguments in JTAG case.

    We can safely check U-boot magic value (0x0) in linux passed via
    r1 register as U-boot pass it from the beginning. So there is no
    backward-compatibility issues.

    Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
    Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/arc/kernel/head.S | 1 +
    arch/arc/kernel/setup.c | 8 ++++++++
    2 files changed, 9 insertions(+)

    diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
    index 1f945d0f40da..208bf2c9e7b0 100644
    --- a/arch/arc/kernel/head.S
    +++ b/arch/arc/kernel/head.S
    @@ -107,6 +107,7 @@ ENTRY(stext)
    ; r2 = pointer to uboot provided cmdline or external DTB in mem
    ; These are handled later in handle_uboot_args()
    st r0, [@uboot_tag]
    + st r1, [@uboot_magic]
    st r2, [@uboot_arg]
    #endif

    diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
    index 3320ca2fe20f..a1218937abd6 100644
    --- a/arch/arc/kernel/setup.c
    +++ b/arch/arc/kernel/setup.c
    @@ -35,6 +35,7 @@ unsigned int intr_to_DE_cnt;

    /* Part of U-boot ABI: see head.S */
    int __initdata uboot_tag;
    +int __initdata uboot_magic;
    char __initdata *uboot_arg;

    const struct machine_desc *machine_desc;
    @@ -484,6 +485,8 @@ static inline bool uboot_arg_invalid(unsigned long addr)
    #define UBOOT_TAG_NONE 0
    #define UBOOT_TAG_CMDLINE 1
    #define UBOOT_TAG_DTB 2
    +/* We always pass 0 as magic from U-boot */
    +#define UBOOT_MAGIC_VALUE 0

    void __init handle_uboot_args(void)
    {
    @@ -499,6 +502,11 @@ void __init handle_uboot_args(void)
    goto ignore_uboot_args;
    }

    + if (uboot_magic != UBOOT_MAGIC_VALUE) {
    + pr_warn(IGNORE_ARGS "non zero uboot magic\n");
    + goto ignore_uboot_args;
    + }
    +
    if (uboot_tag != UBOOT_TAG_NONE &&
    uboot_arg_invalid((unsigned long)uboot_arg)) {
    pr_warn(IGNORE_ARGS "invalid uboot arg: '%px'\n", uboot_arg);
    --
    2.19.1
    \
     
     \ /
      Last update: 2019-03-30 02:09    [W:2.427 / U:0.064 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site