Re: [PATCH -next] riscv: lib: uaccess: fix CSR_STATUS SR_SUM bit

[chenlifu]

在 2022/7/15 11:47, chenlifu 写道:
> > > Since commit 5d8544e2d007 ("RISC-V: Generic library routines and 
> > > assembly")
> > > and commit ebcbd75e3962 ("riscv: Fix the bug in memory access fixup 
> > > code"),
> > > if __clear_user and __copy_user return from an fixup branch,
> > > CSR_STATUS SR_SUM bit will be set, it is a vulnerability, so that
> > > S-mode memory accesses to pages that are accessible by U-mode will 
> > > success.
> > > Disable S-mode access to U-mode memory should clear SR_SUM bit.
> > >
> > > Fixes: 5d8544e2d007 ("RISC-V: Generic library routines and assembly")
> > > Fixes: ebcbd75e3962 ("riscv: Fix the bug in memory access fixup code")
> > >
> > > Signed-off-by: Chen Lifu <chenlifu@xxxxxxxxxx>
> > > ---
> > >   arch/riscv/lib/uaccess.S | 4 ++--
> > >   1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
> > > index 8c475f4da308..ec486e5369d9 100644
> > > --- a/arch/riscv/lib/uaccess.S
> > > +++ b/arch/riscv/lib/uaccess.S
> > > @@ -173,11 +173,11 @@ ENTRY(__asm_copy_from_user)
> > >       ret
> > >       /* Exception fixup code */
> > >   10:
> > >       /* Disable access to user memory */
> > > -    csrs CSR_STATUS, t6
> > > +    csrc CSR_STATUS, t6
> > >       mv a0, t5
> > >       ret
> > >   ENDPROC(__asm_copy_to_user)
> > >   ENDPROC(__asm_copy_from_user)
> > >   EXPORT_SYMBOL(__asm_copy_to_user)
> > > @@ -225,10 +225,10 @@ ENTRY(__clear_user)
> > >       j 3b
> > >       /* Exception fixup code */
> > >   11:
> > >       /* Disable access to user memory */
> > > -    csrs CSR_STATUS, t6
> > > +    csrc CSR_STATUS, t6
> > >       mv a0, a1
> > >       ret
> > >   ENDPROC(__clear_user)
> > >   EXPORT_SYMBOL(__clear_user)
> >
> > friendly ping ...
>
> friendly ping ...
>
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@xxxxxxxxxxxxxxxxxxx
> > http://lists.infradead.org/mailman/listinfo/linux-riscv
> > .
> .

friendly ping ...