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);