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authorEugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>2019-02-25 20:16:01 +0300
committerVineet Gupta <vgupta@synopsys.com>2019-02-25 12:11:01 -0800
commitedb64bca50cd736c6894cc6081d5263c007ce005 (patch)
tree24677adc79af060445efbc7cfe2f598fee7d1536 /arch/arc
parentfbe025c3eaf5f52060c2820eddb7357363db0d27 (diff)
downloadlinux-edb64bca50cd736c6894cc6081d5263c007ce005.tar.bz2
ARC: u-boot args: check that magic number is correct
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>
Diffstat (limited to 'arch/arc')
-rw-r--r--arch/arc/kernel/head.S1
-rw-r--r--arch/arc/kernel/setup.c8
2 files changed, 9 insertions, 0 deletions
diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
index 36774348d23b..8f6e0447dd17 100644
--- a/arch/arc/kernel/head.S
+++ b/arch/arc/kernel/head.S
@@ -111,6 +111,7 @@ 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]
; setup "current" tsk and optionally cache it in dedicated r25
diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
index 2266e4ee4142..ec2fd231ecd9 100644
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -36,6 +36,7 @@ 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;
@@ -504,6 +505,8 @@ 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)
{
@@ -518,6 +521,11 @@ 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);