Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 1 May 2019 12:03:52 -0700 | Subject | Re: [RFC][PATCH] ftrace/x86: Emulate call function while updating in breakpoint handler |
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On Wed, May 1, 2019 at 6:11 AM Peter Zijlstra <peterz@infradead.org> wrote: > > Here goes, compile tested only...
Ugh, two different threads. This has the same bug (same source) as the one Steven posted:
> --- a/arch/x86/entry/entry_32.S > +++ b/arch/x86/entry/entry_32.S > @@ -1479,6 +1479,13 @@ ENTRY(int3) > ASM_CLAC > pushl $-1 # mark this as an int > > + testl $SEGMENT_RPL_MASK, PT_CS(%esp) > + jnz .Lfrom_usermode_no_gap > + .rept 6 > + pushl 5*4(%esp) > + .endr > +.Lfrom_usermode_no_gap:
This will corrupt things horribly if you still use vm86 mode. Checking CS RPL is simply not correct.
Linus
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