[PATCH v3] powerpc: Implement arch_within_stack_frames
From: Nicholas Miehlbradt <hidden>
Date: 2023-02-28 05:45:40
Walks the stack when copy_{to,from}_user address is in the stack to
ensure that the object being copied is entirely a single stack frame and
does not contain stack metadata.
Substantially similar to the x86 implementation. The back chain is used
to traverse the stack and identify stack frame boundaries.
Signed-off-by: Nicholas Miehlbradt <redacted>
---
v3: Move STACK_FRAME_PARAMS macros to ppc_asm.h
Add diagram in comments to show position of pointers into the stack during execution
v2: Rename PARAMETER_SAVE_OFFSET to STACK_FRAME_PARAMS
Add definitions of STACK_FRAME_PARAMS for PPC32 and remove dependancy on PPC64
Ignore the current stack frame and start with it's parent, similar to x86
v1: https://lore.kernel.org/linuxppc-dev/20221214044252.1910657-1-nicholas@linux.ibm.com/
v2: https://lore.kernel.org/linuxppc-dev/20230119053127.17782-1-nicholas@linux.ibm.com/
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/ppc_asm.h | 8 ++++++
arch/powerpc/include/asm/thread_info.h | 38 ++++++++++++++++++++++++++
3 files changed, 47 insertions(+)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2c9cdf1d8761..3ce17f9aa90a 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig@@ -200,6 +200,7 @@ config PPC select HAVE_ARCH_KCSAN if PPC_BOOK3S_64 select HAVE_ARCH_KFENCE if ARCH_SUPPORTS_DEBUG_PAGEALLOC select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET + select HAVE_ARCH_WITHIN_STACK_FRAMES select HAVE_ARCH_KGDB select HAVE_ARCH_MMAP_RND_BITS select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index d2f44612f4b0..1f1a64b780e3 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h@@ -837,4 +837,12 @@ END_FTR_SECTION_NESTED(CPU_FTR_CELL_TB_BUG, CPU_FTR_CELL_TB_BUG, 96) #define BTB_FLUSH(reg) #endif /* CONFIG_PPC_E500 */ +#if defined(CONFIG_PPC64_ELF_ABI_V1) +#define STACK_FRAME_PARAMS 48 +#elif defined(CONFIG_PPC64_ELF_ABI_V2) +#define STACK_FRAME_PARAMS 32 +#elif defined(CONFIG_PPC32) +#define STACK_FRAME_PARAMS 8 +#endif + #endif /* _ASM_POWERPC_PPC_ASM_H */
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index af58f1ed3952..07f1901da8fd 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h@@ -45,6 +45,7 @@ #include <linux/cache.h> #include <asm/processor.h> #include <asm/accounting.h> +#include <asm/ppc_asm.h> #define SLB_PRELOAD_NR 16U /*
@@ -186,6 +187,43 @@ static inline bool test_thread_local_flags(unsigned int flags) #define is_elf2_task() (0) #endif +/* + * Walks up the stack frames to make sure that the specified object is + * entirely contained by a single stack frame. + * + * Returns: + * GOOD_FRAME if within a frame + * BAD_STACK if placed across a frame boundary (or outside stack) + */ +static inline int arch_within_stack_frames(const void * const stack, + const void * const stackend, + const void *obj, unsigned long len) +{ + const void *params; + const void *frame; + + params = *(const void * const *)current_stack_pointer + STACK_FRAME_PARAMS; + frame = **(const void * const * const *)current_stack_pointer; + + /* + * low -----------------------------------------------------------> high + * [backchain][metadata][params][local vars][saved registers][backchain] + * ^------------------------------------^ + * | allows copies only in this region | + * | | + * params frame + * The metadata region contains the saved LR, CR etc. + */ + while (stack <= frame && frame < stackend) { + if (obj + len <= frame) + return obj >= params ? GOOD_FRAME : BAD_STACK; + params = frame + STACK_FRAME_PARAMS; + frame = *(const void * const *)frame; + } + + return BAD_STACK; +} + #endif /* !__ASSEMBLY__ */ #endif /* __KERNEL__ */
--
2.34.1