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authorSami Tolvanen <samitolvanen@google.com>2023-09-28 01:48:04 +0300
committerPalmer Dabbelt <palmer@rivosinc.com>2023-10-28 00:43:10 +0300
commit245561ba6d5de42bf73d501f910b181bc7fa5601 (patch)
treecdb1e0ca68e70b2ba8e0f0258adfdedf28733a9b /drivers/misc
parentc40fef858d002fb027033c572ac8bdf8756a2c6b (diff)
downloadlinux-245561ba6d5de42bf73d501f910b181bc7fa5601.tar.xz
lkdtm: Fix CFI_BACKWARD on RISC-V
On RISC-V, the return address is before the current frame pointer, unlike on most other architectures. Use the correct offset on RISC-V to fix the CFI_BACKWARD test. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Acked-by: Kees Cook <keescook@chromium.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Link: https://lore.kernel.org/r/20230927224757.1154247-14-samitolvanen@google.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'drivers/misc')
-rw-r--r--drivers/misc/lkdtm/cfi.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/drivers/misc/lkdtm/cfi.c b/drivers/misc/lkdtm/cfi.c
index fc28714ae3a6..6a33889d0902 100644
--- a/drivers/misc/lkdtm/cfi.c
+++ b/drivers/misc/lkdtm/cfi.c
@@ -68,12 +68,20 @@ static void lkdtm_CFI_FORWARD_PROTO(void)
#define no_pac_addr(addr) \
((__force __typeof__(addr))((uintptr_t)(addr) | PAGE_OFFSET))
+#ifdef CONFIG_RISCV
+/* https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc#frame-pointer-convention */
+#define FRAME_RA_OFFSET (-1)
+#else
+#define FRAME_RA_OFFSET 1
+#endif
+
/* The ultimate ROP gadget. */
static noinline __no_ret_protection
void set_return_addr_unchecked(unsigned long *expected, unsigned long *addr)
{
/* Use of volatile is to make sure final write isn't seen as a dead store. */
- unsigned long * volatile *ret_addr = (unsigned long **)__builtin_frame_address(0) + 1;
+ unsigned long * volatile *ret_addr =
+ (unsigned long **)__builtin_frame_address(0) + FRAME_RA_OFFSET;
/* Make sure we've found the right place on the stack before writing it. */
if (no_pac_addr(*ret_addr) == expected)
@@ -88,7 +96,8 @@ static noinline
void set_return_addr(unsigned long *expected, unsigned long *addr)
{
/* Use of volatile is to make sure final write isn't seen as a dead store. */
- unsigned long * volatile *ret_addr = (unsigned long **)__builtin_frame_address(0) + 1;
+ unsigned long * volatile *ret_addr =
+ (unsigned long **)__builtin_frame_address(0) + FRAME_RA_OFFSET;
/* Make sure we've found the right place on the stack before writing it. */
if (no_pac_addr(*ret_addr) == expected)