| Message ID | 20151130161811.592c205d8dc7b00f44066a37@linux-foundation.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 11/30/15 4:18 PM, Andrew Morton wrote: > On Mon, 30 Nov 2015 16:04:36 -0800 Kees Cook <keescook@chromium.org> wrote: > >>>>> +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS >>>>> + { >>>>> + .procname = "mmap_rnd_bits", >>>>> + .data = &mmap_rnd_bits, >>>>> + .maxlen = sizeof(mmap_rnd_bits), >>>>> + .mode = 0600, >>>>> + .proc_handler = proc_dointvec_minmax, >>>>> + .extra1 = (void *) &mmap_rnd_bits_min, >>>>> + .extra2 = (void *) &mmap_rnd_bits_max, >>>> >>>> hm, why the typecasts? They're unneeded and are omitted everywhere(?) >>>> else in kernel/sysctl.c. >>> >>> Oh. Casting away constness. >>> >>> What's the thinking here? They can change at any time so they aren't >>> const so we shouldn't declare them to be const? >> >> The _min and _max values shouldn't be changing: they're decided based >> on the various CONFIG options that calculate the valid min/maxes. Only >> mmap_rnd_bits itself should be changing. > > hmpf. > > From: Andrew Morton <akpm@linux-foundation.org> > Subject: include/linux/sysctl.h: make ctl_table.extra1/2 const > > Nothing should be altering these values. Declare the pointed-to values to > be const so we can actually use const values. > > Cc: Kees Cook <keescook@chromium.org> > Cc: Daniel Cashman <dcashman@android.com> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > include/linux/sysctl.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff -puN include/linux/sysctl.h~a include/linux/sysctl.h > --- a/include/linux/sysctl.h~a > +++ a/include/linux/sysctl.h > @@ -111,8 +111,8 @@ struct ctl_table > struct ctl_table *child; /* Deprecated */ > proc_handler *proc_handler; /* Callback for text formatting */ > struct ctl_table_poll *poll; > - void *extra1; > - void *extra2; > + const void *extra1; > + const void *extra2; > }; > > struct ctl_node { > diff -puN kernel/sysctl.c~a kernel/sysctl.c > _ This looks good to me, thanks! I hadn't gone through all of the uses of extra1 and extra2, nor did I think the change herein was conceptually a part of mine, so I casted-away in order to indicate intent, while leaving the change here as a possibility if ctl_table could be altered for all use-cases. Thank You, Dan
Andrew Morton <akpm@linux-foundation.org> writes: > On Mon, 30 Nov 2015 16:04:36 -0800 Kees Cook <keescook@chromium.org> wrote: > >> >> > +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS >> >> > + { >> >> > + .procname = "mmap_rnd_bits", >> >> > + .data = &mmap_rnd_bits, >> >> > + .maxlen = sizeof(mmap_rnd_bits), >> >> > + .mode = 0600, >> >> > + .proc_handler = proc_dointvec_minmax, >> >> > + .extra1 = (void *) &mmap_rnd_bits_min, >> >> > + .extra2 = (void *) &mmap_rnd_bits_max, >> >> >> >> hm, why the typecasts? They're unneeded and are omitted everywhere(?) >> >> else in kernel/sysctl.c. >> > >> > Oh. Casting away constness. >> > >> > What's the thinking here? They can change at any time so they aren't >> > const so we shouldn't declare them to be const? >> >> The _min and _max values shouldn't be changing: they're decided based >> on the various CONFIG options that calculate the valid min/maxes. Only >> mmap_rnd_bits itself should be changing. > > hmpf. > > From: Andrew Morton <akpm@linux-foundation.org> > Subject: include/linux/sysctl.h: make ctl_table.extra1/2 const > > Nothing should be altering these values. Declare the pointed-to values to > be const so we can actually use const values. No large objects except we do seem to have values that are stashed in extra1 that are cast to non-const types. Any chance you will do the work to hunt all of those down and modify the casts to preserve const or to remove the casts entirely? Eric > Cc: Kees Cook <keescook@chromium.org> > Cc: Daniel Cashman <dcashman@android.com> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > include/linux/sysctl.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff -puN include/linux/sysctl.h~a include/linux/sysctl.h > --- a/include/linux/sysctl.h~a > +++ a/include/linux/sysctl.h > @@ -111,8 +111,8 @@ struct ctl_table > struct ctl_table *child; /* Deprecated */ > proc_handler *proc_handler; /* Callback for text formatting */ > struct ctl_table_poll *poll; > - void *extra1; > - void *extra2; > + const void *extra1; > + const void *extra2; > }; > > struct ctl_node { > diff -puN kernel/sysctl.c~a kernel/sysctl.c > _
On Mon, Nov 30, 2015 at 4:18 PM, Andrew Morton <akpm@linux-foundation.org> wrote: > On Mon, 30 Nov 2015 16:04:36 -0800 Kees Cook <keescook@chromium.org> wrote: > >> >> > +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS >> >> > + { >> >> > + .procname = "mmap_rnd_bits", >> >> > + .data = &mmap_rnd_bits, >> >> > + .maxlen = sizeof(mmap_rnd_bits), >> >> > + .mode = 0600, >> >> > + .proc_handler = proc_dointvec_minmax, >> >> > + .extra1 = (void *) &mmap_rnd_bits_min, >> >> > + .extra2 = (void *) &mmap_rnd_bits_max, >> >> >> >> hm, why the typecasts? They're unneeded and are omitted everywhere(?) >> >> else in kernel/sysctl.c. >> > >> > Oh. Casting away constness. >> > >> > What's the thinking here? They can change at any time so they aren't >> > const so we shouldn't declare them to be const? >> >> The _min and _max values shouldn't be changing: they're decided based >> on the various CONFIG options that calculate the valid min/maxes. Only >> mmap_rnd_bits itself should be changing. > > hmpf. > > From: Andrew Morton <akpm@linux-foundation.org> > Subject: include/linux/sysctl.h: make ctl_table.extra1/2 const > > Nothing should be altering these values. Declare the pointed-to values to > be const so we can actually use const values. > > Cc: Kees Cook <keescook@chromium.org> > Cc: Daniel Cashman <dcashman@android.com> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > include/linux/sysctl.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff -puN include/linux/sysctl.h~a include/linux/sysctl.h > --- a/include/linux/sysctl.h~a > +++ a/include/linux/sysctl.h > @@ -111,8 +111,8 @@ struct ctl_table > struct ctl_table *child; /* Deprecated */ > proc_handler *proc_handler; /* Callback for text formatting */ > struct ctl_table_poll *poll; > - void *extra1; > - void *extra2; > + const void *extra1; > + const void *extra2; > }; > > struct ctl_node { > diff -puN kernel/sysctl.c~a kernel/sysctl.c > _ > If allyesconfig builds with this, I'm all for it. :) -Kees
diff -puN include/linux/sysctl.h~a include/linux/sysctl.h --- a/include/linux/sysctl.h~a +++ a/include/linux/sysctl.h @@ -111,8 +111,8 @@ struct ctl_table struct ctl_table *child; /* Deprecated */ proc_handler *proc_handler; /* Callback for text formatting */ struct ctl_table_poll *poll; - void *extra1; - void *extra2; + const void *extra1; + const void *extra2; }; struct ctl_node {