Messages in this thread | | | From | "Aneesh Kumar K.V" <> | Subject | Re: [PATCH v1 4/5] powerpc/fault: Avoid heavy search_exception_tables() verification | Date | Wed, 09 Sep 2020 11:34:31 +0530 |
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Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> search_exception_tables() is an heavy operation, we have to avoid it. > When KUAP is selected, we'll know the fault has been blocked by KUAP. > Otherwise, it behaves just as if the address was already in the TLBs > and no fault was generated. > > Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> > --- > arch/powerpc/mm/fault.c | 20 +++++--------------- > 1 file changed, 5 insertions(+), 15 deletions(-) > > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > index 525e0c2b5406..edde169ba3a6 100644 > --- a/arch/powerpc/mm/fault.c > +++ b/arch/powerpc/mm/fault.c > @@ -214,24 +214,14 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, > if (address >= TASK_SIZE) > return true; > > - if (!is_exec && (error_code & DSISR_PROTFAULT) && > - !search_exception_tables(regs->nip)) { > + // Read/write fault blocked by KUAP is bad, it can never succeed. > + if (bad_kuap_fault(regs, address, is_write)) { > pr_crit_ratelimited("Kernel attempted to access user page (%lx) - exploit attempt? (uid: %d)\n", > - address, > - from_kuid(&init_user_ns, current_uid())); > - } > - > - // Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad > - if (!search_exception_tables(regs->nip)) > - return true;
We still need to keep this ? Without that we detect the lack of exception tables pretty late.
> - > - // Read/write fault in a valid region (the exception table search passed > - // above), but blocked by KUAP is bad, it can never succeed. > - if (bad_kuap_fault(regs, address, is_write)) > + address, from_kuid(&init_user_ns, current_uid())); > return true; > + } > > - // What's left? Kernel fault on user in well defined regions (extable > - // matched), and allowed by KUAP in the faulting context. > + // What's left? Kernel fault on user and allowed by KUAP in the faulting context. > return false; > } > > -- > 2.25.0
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