Messages in this thread | | | Date | Fri, 2 Oct 2020 15:30:30 -0700 | From | Kees Cook <> | Subject | Re: [PATCH V3 1/8] sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs output |
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On Wed, Sep 30, 2020 at 09:22:19PM -0700, Joe Perches wrote: > On Wed, 2020-09-30 at 21:17 -0700, Kees Cook wrote: > > On Wed, Sep 30, 2020 at 01:57:40PM +0200, Greg Kroah-Hartman wrote: > > > Kees, and Rafael, I don't know if you saw this proposal from Joe for > > > sysfs files, questions below: > > > > I'm a fan. I think the use of sprintf() in sysfs might have been one of > > my earliest complaints about unsafe code patterns in the kernel. ;) > [] > > > > + if (WARN(!buf || offset_in_page(buf), > > > > + "invalid sysfs_emit: buf:%p\n", buf)) > > The dump_stack() is also going to emit pointers > so I don't see how it does anything but help > show where the buffer was. It is hashed...
dump_stack() is going to report symbols and register contents.
I was just pointing out that %p has no value here[1]. The interesting states are: "was it NULL?" "how offset was it?". Its actual content won't matter.
-Kees
[1] "New uses of %p should not be added to the kernel" https://www.kernel.org/doc/html/latest/process/deprecated.html#p-format-specifier
-- Kees Cook
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