Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | Re: [PATCH] asm-generic: uaccess: fix up local access_ok() usage | Date | Sat, 13 Jun 2009 22:53:39 +0200 |
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On Saturday 13 June 2009, Mike Frysinger wrote: > There's no reason that I can see to use the short __access_ok() form > directly when the access_ok() is clearer in intent and for more people, > expands to the same C code (i.e. always specify the first field -- access > type). Not all no-mmu systems lack memory protection, so the read/write > could feasibly be checked.
Ah, I didn't consider this. I checked all the architectures and could not find a case where access_ok actually evaluates the the first argument, so I chose the slightly terser variant. I also don't let you override access_ok() at this moment, which means that you don't have a choice to use the generic uaccess.h and still differentiate between read and write accesses.
What I really got wrong was the prototype for __access_ok(), as you showed in your follow-up. I only tested this with the microblaze patch that overrides __access_ok() with an architecture specific version that gets this part right.
Would this simpler patch help you as well?
--- a/include/asm-generic/uaccess.h +++ b/include/asm-generic/uaccess.h @@ -37,14 +37,14 @@ static inline void set_fs(mm_segment_t fs) #define VERIFY_READ 0 #define VERIFY_WRITE 1 -#define access_ok(type, addr, size) __access_ok((unsigned long)(addr),(size)) +#define access_ok(type, addr, size) __access_ok((addr), (size)) /* * The architecture should really override this if possible, at least * doing a check on the get_fs() */ #ifndef __access_ok -static inline int __access_ok(unsigned long addr, unsigned long size) +static inline int __access_ok(void __user *ptr, unsigned long size) { return 1; } It may not be clearer in intent, but it's what the majority (by a small margin) of architecture do anyway.
> Also, the strnlen_user() function was missing a access_ok() check on the > pointer given. We've had cases on Blackfin systems where test cases > caused kernel crashes here because userspace passed up a NULL/-1 pointer > and the kernel gladly attempted to run strlen() on it.
Right, well spotted. I'll take this fix as a separate patch, ok?
Arnd <><
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