diff options
Diffstat (limited to 'arch/x86/kernel/traps.c')
| -rw-r--r-- | arch/x86/kernel/traps.c | 44 |
1 files changed, 33 insertions, 11 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index cb324cc1fd99..bcf1dedc1d00 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -732,13 +732,23 @@ DEFINE_IDTENTRY(exc_bounds) enum kernel_gp_hint { GP_NO_HINT, GP_NON_CANONICAL, - GP_CANONICAL + GP_CANONICAL, + GP_LASS_VIOLATION, + GP_NULL_POINTER, +}; + +static const char * const kernel_gp_hint_help[] = { + [GP_NON_CANONICAL] = "probably for non-canonical address", + [GP_CANONICAL] = "maybe for address", + [GP_LASS_VIOLATION] = "probably LASS violation for address", + [GP_NULL_POINTER] = "kernel NULL pointer dereference", }; /* * When an uncaught #GP occurs, try to determine the memory address accessed by * the instruction and return that address to the caller. Also, try to figure - * out whether any part of the access to that address was non-canonical. + * out whether any part of the access to that address was non-canonical or + * across privilege levels. */ static enum kernel_gp_hint get_kernel_gp_address(struct pt_regs *regs, unsigned long *addr) @@ -760,14 +770,28 @@ static enum kernel_gp_hint get_kernel_gp_address(struct pt_regs *regs, return GP_NO_HINT; #ifdef CONFIG_X86_64 + /* Operand is in the kernel half */ + if (*addr >= ~__VIRTUAL_MASK) + return GP_CANONICAL; + + /* The last byte of the operand is not in the user canonical half */ + if (*addr + insn.opnd_bytes - 1 > __VIRTUAL_MASK) + return GP_NON_CANONICAL; + /* - * Check that: - * - the operand is not in the kernel half - * - the last byte of the operand is not in the user canonical half + * A NULL pointer dereference usually causes a #PF. However, it + * can result in a #GP when LASS is active. Provide the same + * hint in the rare case that the condition is hit without LASS. */ - if (*addr < ~__VIRTUAL_MASK && - *addr + insn.opnd_bytes - 1 > __VIRTUAL_MASK) - return GP_NON_CANONICAL; + if (*addr < PAGE_SIZE) + return GP_NULL_POINTER; + + /* + * Assume that LASS caused the exception, because the address is + * canonical and in the user half. + */ + if (cpu_feature_enabled(X86_FEATURE_LASS)) + return GP_LASS_VIOLATION; #endif return GP_CANONICAL; @@ -930,9 +954,7 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) if (hint != GP_NO_HINT) snprintf(desc, sizeof(desc), GPFSTR ", %s 0x%lx", - (hint == GP_NON_CANONICAL) ? "probably for non-canonical address" - : "maybe for address", - gp_addr); + kernel_gp_hint_help[hint], gp_addr); /* * KASAN is interested only in the non-canonical case, clear it |