From: Carl Love <[EMAIL PROTECTED]>
Fix the 64 bit user code backtrace which currently may hang the system.
Signed-off-by: Carl Love <[EMAIL PROTECTED]>
Cc: Maynard Johnson <[EMAIL PROTECTED]>
On Thu, 15 May 2008 10:20:44 +1000
Michael Ellerman <[EMAIL PROTECTED]> wrote:
>
> __copy_from_user_inatomic() accepts any value for n, it just has a
> special case for 1, 2, 4 and 8 - but it should still work for other
> values.
>
> The old code copied 24 bytes from sp, and the new code copies 8 bytes
> from sp and 8 bytes from sp + 16 - so I don't see where the 48 bytes
> comes in to it?
>
> \ufeffAlso the comment is a little hard to parse, I think you mean "Issue:
> the ..", but I read "Issue" as a verb in that sentence. And "Don't read
> more then" should be "than".
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
arch/powerpc/oprofile/backtrace.c | 33 ++++++++++++++++++++++------
1 file changed, 27 insertions(+), 6 deletions(-)
diff -puN
arch/powerpc/oprofile/backtrace.c~powerpc-fix-for-oprofile-callgraph-for-power-64-bit-user-apps
arch/powerpc/oprofile/backtrace.c
---
a/arch/powerpc/oprofile/backtrace.c~powerpc-fix-for-oprofile-callgraph-for-power-64-bit-user-apps
+++ a/arch/powerpc/oprofile/backtrace.c
@@ -53,19 +53,40 @@ static unsigned int user_getsp32(unsigne
#ifdef CONFIG_PPC64
static unsigned long user_getsp64(unsigned long sp, int is_first)
{
- unsigned long stack_frame[3];
+ unsigned long stk_frm_lr;
+ unsigned long stk_frm_sp;
+ unsigned long size;
+
+ /* Issue the __copy_from_user_inatomic() third argument currently
+ * only takes sizes 1, 2, 4 or 8 bytes. Don't read more then the
+ * first 48 bytes of the stack frame. That is all that is
+ * guaranteed to exist. Reading more may cause the system to hang.
+ *
+ * 64 bit stack frame layout:
+ * 0-7 bytes is the pointer to previous stack
+ * 8-15 bytes condition register save area
+ * 16-23 bytes link register save area
+ */
+ size = sizeof(unsigned long);
+ if (!access_ok(VERIFY_READ, (void __user *)sp, size))
+ return 0;
- if (!access_ok(VERIFY_READ, (void __user *)sp, sizeof(stack_frame)))
+ if (__copy_from_user_inatomic(&stk_frm_sp, (void __user *)sp,
+ size))
return 0;
- if (__copy_from_user_inatomic(stack_frame, (void __user *)sp,
- sizeof(stack_frame)))
+ /* get the LR from the user stack */
+ if (!access_ok(VERIFY_READ, (void __user *)(sp+16), size))
+ return 0;
+
+ if (__copy_from_user_inatomic(&stk_frm_lr, (void __user *)(sp+16),
+ size))
return 0;
if (!is_first)
- oprofile_add_trace(STACK_LR64(stack_frame));
+ oprofile_add_trace(stk_frm_lr);
- return STACK_SP(stack_frame);
+ return stk_frm_sp;
}
#endif
_
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