Re: [PATCH] misc: tifm: Remove VLA
On 04/10/2018 12:57 AM, Arnd Bergmann wrote: On Mon, Apr 9, 2018 at 11:07 PM, Laura Abbott wrote: There's an ongoing effort to remove VLAs[1] from the kernel to eventually turn on -Wvla. The single VLA can either take a value of 2 or 4 so switch to the upper bound. [1] https://lkml.org/lkml/2018/3/7/621 Signed-off-by: Laura Abbott --- drivers/misc/tifm_7xx1.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/misc/tifm_7xx1.c b/drivers/misc/tifm_7xx1.c index e5f108713dd8..690eaaea5ce4 100644 --- a/drivers/misc/tifm_7xx1.c +++ b/drivers/misc/tifm_7xx1.c @@ -239,7 +239,8 @@ static int tifm_7xx1_resume(struct pci_dev *dev) unsigned long timeout; unsigned int good_sockets = 0, bad_sockets = 0; unsigned long flags; - unsigned char new_ids[fm->num_sockets]; + /* Maximum number of entries is 4 */ + unsigned char new_ids[4]; DECLARE_COMPLETION_ONSTACK(finish_resume); I like the idea of removing all the VLAs, but this one appears to make the code less robust rather than more: In case of an unexpected fm->num_sockets value, we now not only overflow the kernel stack area but also the local variable into the neighboring stack slots. Maybe add an extra overflow check? Sure. Arnd diff --git a/drivers/misc/tifm_7xx1.c b/drivers/misc/tifm_7xx1.c index e5f108713dd8..c702cd92d396 100644 --- a/drivers/misc/tifm_7xx1.c +++ b/drivers/misc/tifm_7xx1.c @@ -239,9 +239,12 @@ static int tifm_7xx1_resume(struct pci_dev *dev) unsigned long timeout; unsigned int good_sockets = 0, bad_sockets = 0; unsigned long flags; - unsigned char new_ids[fm->num_sockets]; + /* Maximum number of entries is 4 */ + unsigned char new_ids[4]; DECLARE_COMPLETION_ONSTACK(finish_resume); + if (WARN_ON(fm->num_sockets > ARRAY_SIZE(new_ids))) + return -ENXIO; + pci_set_power_state(dev, PCI_D0); pci_restore_state(dev); rc = pci_enable_device(dev);
Re: [PATCH] misc: tifm: Remove VLA
On Mon, Apr 9, 2018 at 11:07 PM, Laura Abbott wrote: > There's an ongoing effort to remove VLAs[1] from the kernel to eventually > turn on -Wvla. The single VLA can either take a value of 2 or 4 so switch > to the upper bound. > > [1] https://lkml.org/lkml/2018/3/7/621 > > Signed-off-by: Laura Abbott > --- > drivers/misc/tifm_7xx1.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/misc/tifm_7xx1.c b/drivers/misc/tifm_7xx1.c > index e5f108713dd8..690eaaea5ce4 100644 > --- a/drivers/misc/tifm_7xx1.c > +++ b/drivers/misc/tifm_7xx1.c > @@ -239,7 +239,8 @@ static int tifm_7xx1_resume(struct pci_dev *dev) > unsigned long timeout; > unsigned int good_sockets = 0, bad_sockets = 0; > unsigned long flags; > - unsigned char new_ids[fm->num_sockets]; > + /* Maximum number of entries is 4 */ > + unsigned char new_ids[4]; > DECLARE_COMPLETION_ONSTACK(finish_resume); > I like the idea of removing all the VLAs, but this one appears to make the code less robust rather than more: In case of an unexpected fm->num_sockets value, we now not only overflow the kernel stack area but also the local variable into the neighboring stack slots. Maybe add an extra overflow check? Arnd diff --git a/drivers/misc/tifm_7xx1.c b/drivers/misc/tifm_7xx1.c index e5f108713dd8..c702cd92d396 100644 --- a/drivers/misc/tifm_7xx1.c +++ b/drivers/misc/tifm_7xx1.c @@ -239,9 +239,12 @@ static int tifm_7xx1_resume(struct pci_dev *dev) unsigned long timeout; unsigned int good_sockets = 0, bad_sockets = 0; unsigned long flags; - unsigned char new_ids[fm->num_sockets]; + /* Maximum number of entries is 4 */ + unsigned char new_ids[4]; DECLARE_COMPLETION_ONSTACK(finish_resume); + if (WARN_ON(fm->num_sockets > ARRAY_SIZE(new_ids))) + return -ENXIO; + pci_set_power_state(dev, PCI_D0); pci_restore_state(dev); rc = pci_enable_device(dev);
