Messages in this thread | | | Date | Thu, 11 Apr 2013 14:37:39 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH 5/5] keep /dev/kmem from triggering BUG_ON() with DEBUG_VIRTUAL |
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Some more compiler warnings. Btw, I'm building 32-bit only for now - no 64-bit testing yet.
On Wed, Apr 10, 2013 at 04:32:56PM -0700, Dave Hansen wrote: > > /dev/kmem can essentially be used to make the kernel call __pa() > on any address. But, with DEBUG_VIRTUAL, we are now ensuring > that when __pa() is only called on addresses for which its > results are correct. For everything else, we BUG_ON(). > > What this means is that a hapless /dev/kmem user can > unintentionally make the kernel BUG_ON(). > > This adds a function, is_kernel_linear_vaddr() to the /dev/kmem > code to ensure that __pa() will not BUG_ON(). It will, instead, > return an error up to the user. > > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> > --- > > linux.git-davehans/arch/x86/mm/pageattr.c | 19 +++++++++++++++++++ > linux.git-davehans/drivers/char/mem.c | 8 ++++++++ > linux.git-davehans/include/linux/mmdebug.h | 2 ++ > 3 files changed, 29 insertions(+) > > diff -puN arch/x86/mm/pageattr.c~make-devmem-work-on-highmem3b arch/x86/mm/pageattr.c > --- linux.git/arch/x86/mm/pageattr.c~make-devmem-work-on-highmem3b 2013-04-10 16:23:45.780087708 -0700 > +++ linux.git-davehans/arch/x86/mm/pageattr.c 2013-04-10 16:23:45.786087714 -0700 > @@ -406,6 +406,25 @@ phys_addr_t slow_virt_to_phys(void *virt > } > EXPORT_SYMBOL_GPL(slow_virt_to_phys); > > +#ifdef CONFIG_DEBUG_VIRTUAL > +int is_kernel_linear_vaddr(void *kernel_vaddr) > +{ > + int err; > + unsigned long pte_walk_paddr; > + unsigned long linear_paddr = __pa_nodebug(kernel_vaddr); > + > + err = kernel_lookup_vaddr(kernel_vaddr, &pte_walk_paddr);
arch/x86/mm/pageattr.c: In function ‘is_kernel_linear_vaddr’: arch/x86/mm/pageattr.c:416:2: warning: passing argument 2 of ‘kernel_lookup_vaddr’ from incompatible pointer type [enabled by default] arch/x86/mm/pageattr.c:366:5: note: expected ‘phys_addr_t *’ but argument is of type ‘long unsigned int *’
> + /* if there is no pte, it can not be in the normal linear map */ > + if (err) > + return 0; > + /* is there is a pte which does not match the linear layout? */ > + if (pte_walk_paddr != linear_paddr) > + return 0; > + > + return 1; > +} > +#endif /* CONFIG_DEBUG_VIRTUAL */ > + > /* > * Set the new pmd in all the pgds we know about: > */ > diff -puN drivers/char/mem.c~make-devmem-work-on-highmem3b drivers/char/mem.c > --- linux.git/drivers/char/mem.c~make-devmem-work-on-highmem3b 2013-04-10 16:23:45.781087709 -0700 > +++ linux.git-davehans/drivers/char/mem.c 2013-04-10 16:23:45.787087715 -0700 > @@ -357,6 +357,14 @@ static int mmap_kmem(struct file *file, > if (!pfn_valid(pfn)) > return -EIO; > > + /* > + * the __pa() calculation below only makes sense if the kernel's > + * pagetables are set up in the way that __pa() expects. Otherwise, > + * we are effectively mapping random memory in to place. > + */ > + if (!is_kernel_linear_vaddr(kernel_vaddr))
Ditto:
drivers/char/mem.c:365:2: warning: passing argument 1 of ‘is_kernel_linear_vaddr’ makes pointer from integer without a cast [enabled by default]
> + return -EIO; > + > /* Turn a kernel-virtual address into a physical page frame */ > pfn = __pa(kernel_vaddr) >> PAGE_SHIFT; > > diff -puN include/linux/mmdebug.h~make-devmem-work-on-highmem3b include/linux/mmdebug.h > --- linux.git/include/linux/mmdebug.h~make-devmem-work-on-highmem3b 2013-04-10 16:23:45.783087711 -0700 > +++ linux.git-davehans/include/linux/mmdebug.h 2013-04-10 16:23:45.787087715 -0700 > @@ -9,8 +9,10 @@ > > #ifdef CONFIG_DEBUG_VIRTUAL > #define VIRTUAL_BUG_ON(cond) BUG_ON(cond) > +extern int is_kernel_linear_vaddr(void *kernel_vaddr); > #else > #define VIRTUAL_BUG_ON(cond) do { } while (0) > +static inline int is_kernel_linear_vaddr(void *kernel_vaddr) { return 1; }a
In file included from include/linux/gfp.h:8:0, from include/linux/mm.h:8, from drivers/char/mem.c:11: include/linux/mmdebug.h:12:12: note: expected ‘void *’ but argument is of type ‘long unsigned int’ In file included from include/linux/gfp.h:4:0, from include/linux/mm.h:8, from drivers/char/mem.c:11: include/linux/mmzone.h:1187:6: warning: ‘pfn’ may be used uninitialized in this function [-Wuninitialized] drivers/char/mem.c:340:16: note: ‘pfn’ was declared here
HTH.
-- Regards/Gruss, Boris.
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