Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH v11 18/19] module: fix types of device tables aliases | Date | Mon, 16 Feb 2015 13:14:02 +1030 |
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Andrey Ryabinin <a.ryabinin@samsung.com> writes: > MODULE_DEVICE_TABLE() macro used to create aliases to device tables. > Normally alias should have the same type as aliased symbol. > > Device tables are arrays, so they have 'struct type##_device_id[x]' > types. Alias created by MODULE_DEVICE_TABLE() will have non-array type - > 'struct type##_device_id'. > > This inconsistency confuses compiler, it could make a wrong > assumption about variable's size which leads KASan to > produce a false positive report about out of bounds access.
Hmm, as Andrew Morton points out, this breaks some usage; if we just fix the type (struct type##_device_id[]) will that work instead?
I'm guessing not, since typeof(x) will presumably preserve sizing information?
Cheers, Rusty.
> > For every global variable compiler calls __asan_register_globals() > passing information about global variable (address, size, size with > redzone, name ...) __asan_register_globals() poison symbols > redzone to detect possible out of bounds accesses. > > When symbol has an alias __asan_register_globals() will be called > as for symbol so for alias. Compiler determines size of variable by > size of variable's type. Alias and symbol have the same address, > so if alias have the wrong size part of memory that actually belongs > to the symbol could be poisoned as redzone of alias symbol. > > By fixing type of alias symbol we will fix size of it, so > __asan_register_globals() will not poison valid memory. > > Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com> > --- > include/linux/module.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/module.h b/include/linux/module.h > index b653d7c..42999fe 100644 > --- a/include/linux/module.h > +++ b/include/linux/module.h > @@ -135,7 +135,7 @@ void trim_init_extable(struct module *m); > #ifdef MODULE > /* Creates an alias so file2alias.c can find device table. */ > #define MODULE_DEVICE_TABLE(type, name) \ > - extern const struct type##_device_id __mod_##type##__##name##_device_table \ > +extern const typeof(name) __mod_##type##__##name##_device_table \ > __attribute__ ((unused, alias(__stringify(name)))) > #else /* !MODULE */ > #define MODULE_DEVICE_TABLE(type, name) > -- > 2.2.2
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