| Message ID | 20230613210400.never.078-kees@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | usb: ch9: Replace 1-element array with flexible array | expand |
On Tue, Jun 13, 2023 at 02:04:04PM -0700, Kees Cook wrote: > With "-fstrict-flex-arrays=3" enabled, UBSAN_BOUNDS no longer pretends > 1-element arrays are unbounded. Walking wData will trigger a warning, > so make it a proper flexible array. Add a union to keep the struct size > identical for userspace in case anything was depending on the old size. > > Reported-by: kernel test robot <oliver.sang@intel.com> > Closes: https://lore.kernel.org/oe-lkp/202306102333.8f5a7443-oliver.sang@intel.com > Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") I always have mixed feelings about a 'Fixes' tag applied to a commit like this (one that enables a compiler option that avoids the introduction of buggy code), when we are addressing the potentially buggy code that the option is inteded to prevent. (thinkingface) > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: kernel test robot <lkp@intel.com> > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: "Jó Ágila Bitsch" <jgilab@gmail.com> > Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> Thanks! -- Gustavo > --- > include/uapi/linux/usb/ch9.h | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h > index b17e3a21b15f..82ec6af71a1d 100644 > --- a/include/uapi/linux/usb/ch9.h > +++ b/include/uapi/linux/usb/ch9.h > @@ -376,7 +376,10 @@ struct usb_string_descriptor { > __u8 bLength; > __u8 bDescriptorType; > > - __le16 wData[1]; /* UTF-16LE encoded */ > + union { > + __le16 legacy_padding; > + __DECLARE_FLEX_ARRAY(__le16, wData); /* UTF-16LE encoded */ > + }; > } __attribute__ ((packed)); > > /* note that "string" zero is special, it holds language codes that > -- > 2.34.1 >
On Tue, Jun 13, 2023 at 04:52:08PM -0600, Gustavo A. R. Silva wrote: > On Tue, Jun 13, 2023 at 02:04:04PM -0700, Kees Cook wrote: > > With "-fstrict-flex-arrays=3" enabled, UBSAN_BOUNDS no longer pretends > > 1-element arrays are unbounded. Walking wData will trigger a warning, > > so make it a proper flexible array. Add a union to keep the struct size > > identical for userspace in case anything was depending on the old size. > > > > Reported-by: kernel test robot <oliver.sang@intel.com> > > Closes: https://lore.kernel.org/oe-lkp/202306102333.8f5a7443-oliver.sang@intel.com > > Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") > > I always have mixed feelings about a 'Fixes' tag applied to a commit > like this (one that enables a compiler option that avoids the introduction > of buggy code), when we are addressing the potentially buggy code that > the option is inteded to prevent. (thinkingface) Yeah, the original code here is not incorrect, it's that you added a new build warning, so this is more like an "update" :) > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > Cc: kernel test robot <lkp@intel.com> > > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> > > Cc: Dan Williams <dan.j.williams@intel.com> > > Cc: "Jó Ágila Bitsch" <jgilab@gmail.com> > > Signed-off-by: Kees Cook <keescook@chromium.org> > > Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> Odd that checkpatch.pl doesn't cc: the usb lists for this file. I'll go update the MAINTAINERS file with this location... thanks, greg k-h
On Tue, Jun 13, 2023 at 04:52:08PM -0600, Gustavo A. R. Silva wrote: > On Tue, Jun 13, 2023 at 02:04:04PM -0700, Kees Cook wrote: > > With "-fstrict-flex-arrays=3" enabled, UBSAN_BOUNDS no longer pretends > > 1-element arrays are unbounded. Walking wData will trigger a warning, > > so make it a proper flexible array. Add a union to keep the struct size > > identical for userspace in case anything was depending on the old size. > > > > Reported-by: kernel test robot <oliver.sang@intel.com> > > Closes: https://lore.kernel.org/oe-lkp/202306102333.8f5a7443-oliver.sang@intel.com > > Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") > > I always have mixed feelings about a 'Fixes' tag applied to a commit > like this (one that enables a compiler option that avoids the introduction > of buggy code), when we are addressing the potentially buggy code that > the option is inteded to prevent. (thinkingface) Yeah, I've been on the fence about this too. Since it's fixing a (modern) coding style issue, there's nothing wrong technically. i.e. I can't say "Fixes: ...usb commit..." since this isn't a bug. But it's fixing a warning introduced by the fstrict-flex-arrays=3, and tracking those issues is useful. But, it's not really fixing _that_ commit, as it's doing exactly what it should be doing. So, perhaps, in the future I can just mention it more directly in the commit log without a Fixes tag. For example, this should probably have been written as: Since commit df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3"), UBSAN_BOUNDS no longer pretends 1-element arrays are unbounded. Walking wData will trigger a warning, so make it a proper flexible array. Add a union to keep the struct size identical for userspace in case anything was depending on the old size. Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202306102333.8f5a7443-oliver.sang@intel.com -Kees
diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h index b17e3a21b15f..82ec6af71a1d 100644 --- a/include/uapi/linux/usb/ch9.h +++ b/include/uapi/linux/usb/ch9.h @@ -376,7 +376,10 @@ struct usb_string_descriptor { __u8 bLength; __u8 bDescriptorType; - __le16 wData[1]; /* UTF-16LE encoded */ + union { + __le16 legacy_padding; + __DECLARE_FLEX_ARRAY(__le16, wData); /* UTF-16LE encoded */ + }; } __attribute__ ((packed)); /* note that "string" zero is special, it holds language codes that
With "-fstrict-flex-arrays=3" enabled, UBSAN_BOUNDS no longer pretends 1-element arrays are unbounded. Walking wData will trigger a warning, so make it a proper flexible array. Add a union to keep the struct size identical for userspace in case anything was depending on the old size. Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202306102333.8f5a7443-oliver.sang@intel.com Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: kernel test robot <lkp@intel.com> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: "Jó Ágila Bitsch" <jgilab@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org> --- include/uapi/linux/usb/ch9.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)