| Message ID | 20210803181135.22298-1-novikov@ispras.ru (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | platform/x86: intel_pmc_core: Fix potential buffer overflows | expand |
On Tue, Aug 3, 2021 at 9:21 PM Evgeny Novikov <novikov@ispras.ru> wrote: > > It looks like pmc_core_get_low_power_modes() mixes up modes and > priorities. In addition to invalid behavior, potentially this can > cause buffer overflows since the driver reads priorities from the > register and then it uses them as indexes for array lpm_priority > that can contain 8 elements at most. The patch swaps modes and > priorities. > > Found by Linux Driver Verification project (linuxtesting.org). Seems legit. Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > Fixes: 005125bfd70e ("platform/x86: intel_pmc_core: Handle sub-states generically") > Signed-off-by: Evgeny Novikov <novikov@ispras.ru> > --- > drivers/platform/x86/intel_pmc_core.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/platform/x86/intel_pmc_core.c b/drivers/platform/x86/intel_pmc_core.c > index b0e486a6bdfb..667b3df03764 100644 > --- a/drivers/platform/x86/intel_pmc_core.c > +++ b/drivers/platform/x86/intel_pmc_core.c > @@ -1469,8 +1469,8 @@ static void pmc_core_get_low_power_modes(struct pmc_dev *pmcdev) > int pri0 = GENMASK(3, 0) & priority; > int pri1 = (GENMASK(7, 4) & priority) >> 4; > > - lpm_priority[pri0] = mode; > - lpm_priority[pri1] = mode + 1; > + lpm_priority[mode] = pri0; I would write it as + 0, but up to you and maintainers. > + lpm_priority[mode + 1] = pri1; > } > > /* > -- > 2.26.2 >
On Tue, Aug 3, 2021 at 9:26 PM Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > On Tue, Aug 3, 2021 at 9:21 PM Evgeny Novikov <novikov@ispras.ru> wrote: > > > > It looks like pmc_core_get_low_power_modes() mixes up modes and > > priorities. In addition to invalid behavior, potentially this can > > cause buffer overflows since the driver reads priorities from the > > register and then it uses them as indexes for array lpm_priority > > that can contain 8 elements at most. The patch swaps modes and > > priorities. > > > > Found by Linux Driver Verification project (linuxtesting.org). > > Seems legit. Hold on, but then it follows with another loop where actually it reads modes by priority index. Can you elaborate what exactly is the problem you think?
Hi, On Tue, 2021-08-03 at 21:11 +0300, Evgeny Novikov wrote: > It looks like pmc_core_get_low_power_modes() mixes up modes and > priorities. In addition to invalid behavior, potentially this can > cause buffer overflows since the driver reads priorities from the > register and then it uses them as indexes for array lpm_priority > that can contain 8 elements at most. The patch swaps modes and > priorities. > > Found by Linux Driver Verification project (linuxtesting.org). > > Fixes: 005125bfd70e ("platform/x86: intel_pmc_core: Handle sub-states > generically") > Signed-off-by: Evgeny Novikov <novikov@ispras.ru> > --- > drivers/platform/x86/intel_pmc_core.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/platform/x86/intel_pmc_core.c > b/drivers/platform/x86/intel_pmc_core.c > index b0e486a6bdfb..667b3df03764 100644 > --- a/drivers/platform/x86/intel_pmc_core.c > +++ b/drivers/platform/x86/intel_pmc_core.c > @@ -1469,8 +1469,8 @@ static void pmc_core_get_low_power_modes(struct > pmc_dev *pmcdev) > int pri0 = GENMASK(3, 0) & priority; > int pri1 = (GENMASK(7, 4) & priority) >> 4; > > - lpm_priority[pri0] = mode; > - lpm_priority[pri1] = mode + 1; Agree with the buffer overflow concern if hardware were to return an incorrect value. But the assignment and indexing are correct. The list was made to get the modes in priority order which is the order of states the hardware will attempt to use if able. I'll submit a patch for the overflow. David > + lpm_priority[mode] = pri0; > + lpm_priority[mode + 1] = pri1; > } > > /*
On 03.08.2021 21:30, Andy Shevchenko wrote: > On Tue, Aug 3, 2021 at 9:26 PM Andy Shevchenko > <andy.shevchenko@gmail.com> wrote: >> On Tue, Aug 3, 2021 at 9:21 PM Evgeny Novikov <novikov@ispras.ru> wrote: >>> It looks like pmc_core_get_low_power_modes() mixes up modes and >>> priorities. In addition to invalid behavior, potentially this can >>> cause buffer overflows since the driver reads priorities from the >>> register and then it uses them as indexes for array lpm_priority >>> that can contain 8 elements at most. The patch swaps modes and >>> priorities. >>> >>> Found by Linux Driver Verification project (linuxtesting.org). >> Seems legit. > Hold on, but then it follows with another loop where actually it reads > modes by priority index. Can you elaborate what exactly is the problem > you think? > I agree with you and David that my fix was not valid from the functional point of view. Indeed, some issues can happen if something unexpected will be read from the register. For instance, for priority equals to 255 you will have pri0 = 15 and prio1 = 15. Obviously, you can not access the lpm_priority array consisting of just 8 elements by these indexes. Best regards, Evgeny Novikov
diff --git a/drivers/platform/x86/intel_pmc_core.c b/drivers/platform/x86/intel_pmc_core.c index b0e486a6bdfb..667b3df03764 100644 --- a/drivers/platform/x86/intel_pmc_core.c +++ b/drivers/platform/x86/intel_pmc_core.c @@ -1469,8 +1469,8 @@ static void pmc_core_get_low_power_modes(struct pmc_dev *pmcdev) int pri0 = GENMASK(3, 0) & priority; int pri1 = (GENMASK(7, 4) & priority) >> 4; - lpm_priority[pri0] = mode; - lpm_priority[pri1] = mode + 1; + lpm_priority[mode] = pri0; + lpm_priority[mode + 1] = pri1; } /*
It looks like pmc_core_get_low_power_modes() mixes up modes and priorities. In addition to invalid behavior, potentially this can cause buffer overflows since the driver reads priorities from the register and then it uses them as indexes for array lpm_priority that can contain 8 elements at most. The patch swaps modes and priorities. Found by Linux Driver Verification project (linuxtesting.org). Fixes: 005125bfd70e ("platform/x86: intel_pmc_core: Handle sub-states generically") Signed-off-by: Evgeny Novikov <novikov@ispras.ru> --- drivers/platform/x86/intel_pmc_core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)