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Subject[RFC][PATCH 01/22] x86 user stack frame reads: switch to explicit __get_user()
Date
From: Al Viro <viro@zeniv.linux.org.uk>

rather than relying upon the magic in raw_copy_from_user()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
arch/x86/events/core.c | 27 +++++++--------------------
arch/x86/include/asm/uaccess.h | 9 ---------
arch/x86/kernel/stacktrace.c | 6 ++++--
3 files changed, 11 insertions(+), 31 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 3bb738f5a472..a619763e96e1 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2490,7 +2490,7 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *ent
/* 32-bit process in 64-bit kernel. */
unsigned long ss_base, cs_base;
struct stack_frame_ia32 frame;
- const void __user *fp;
+ const struct stack_frame_ia32 __user *fp;

if (!test_thread_flag(TIF_IA32))
return 0;
@@ -2501,18 +2501,12 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *ent
fp = compat_ptr(ss_base + regs->bp);
pagefault_disable();
while (entry->nr < entry->max_stack) {
- unsigned long bytes;
- frame.next_frame = 0;
- frame.return_address = 0;
-
if (!valid_user_frame(fp, sizeof(frame)))
break;

- bytes = __copy_from_user_nmi(&frame.next_frame, fp, 4);
- if (bytes != 0)
+ if (__get_user(frame.next_frame, &fp->next_frame))
break;
- bytes = __copy_from_user_nmi(&frame.return_address, fp+4, 4);
- if (bytes != 0)
+ if (__get_user(frame.return_address, &fp->return_address))
break;

perf_callchain_store(entry, cs_base + frame.return_address);
@@ -2533,7 +2527,7 @@ void
perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
{
struct stack_frame frame;
- const unsigned long __user *fp;
+ const struct stack_frame __user *fp;

if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
/* TODO: We don't support guest os callchain now */
@@ -2546,7 +2540,7 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs
if (regs->flags & (X86_VM_MASK | PERF_EFLAGS_VM))
return;

- fp = (unsigned long __user *)regs->bp;
+ fp = (void __user *)regs->bp;

perf_callchain_store(entry, regs->ip);

@@ -2558,19 +2552,12 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs

pagefault_disable();
while (entry->nr < entry->max_stack) {
- unsigned long bytes;
-
- frame.next_frame = NULL;
- frame.return_address = 0;
-
if (!valid_user_frame(fp, sizeof(frame)))
break;

- bytes = __copy_from_user_nmi(&frame.next_frame, fp, sizeof(*fp));
- if (bytes != 0)
+ if (__get_user(frame.next_frame, &fp->next_frame))
break;
- bytes = __copy_from_user_nmi(&frame.return_address, fp + 1, sizeof(*fp));
- if (bytes != 0)
+ if (__get_user(frame.return_address, &fp->return_address))
break;

perf_callchain_store(entry, frame.return_address);
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 61d93f062a36..ab8eab43a8a2 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -695,15 +695,6 @@ extern struct movsl_mask {
#endif

/*
- * We rely on the nested NMI work to allow atomic faults from the NMI path; the
- * nested NMI paths are careful to preserve CR2.
- *
- * Caller must use pagefault_enable/disable, or run in interrupt context,
- * and also do a uaccess_ok() check
- */
-#define __copy_from_user_nmi __copy_from_user_inatomic
-
-/*
* The "unsafe" user accesses aren't really "unsafe", but the naming
* is a big fat warning: you have to not only do the access_ok()
* checking before using them, but you have to surround them with the
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 2d6898c2cb64..6ad43fc44556 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -96,7 +96,8 @@ struct stack_frame_user {
};

static int
-copy_stack_frame(const void __user *fp, struct stack_frame_user *frame)
+copy_stack_frame(const struct stack_frame_user __user *fp,
+ struct stack_frame_user *frame)
{
int ret;

@@ -105,7 +106,8 @@ copy_stack_frame(const void __user *fp, struct stack_frame_user *frame)

ret = 1;
pagefault_disable();
- if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
+ if (__get_user(frame->next_fp, &fp->next_fp) ||
+ __get_user(frame->ret_addr, &fp->ret_addr))
ret = 0;
pagefault_enable();

--
2.11.0
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