Messages in this thread | | | Date | Thu, 01 Sep 2011 09:30:06 +1000 | From | Ryan Mallon <> | Subject | Re: [PATCH 01/24] fix default __strnlen_user macro |
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On 01/09/11 07:26, Mark Salter wrote: > The existing __strnlen_user macro simply resolved to strnlen. However, the > count returned by strnlen_user should include the NULL byte. This patch > fixes the __strnlen_user macro to include the NULL byte in the count. > > Signed-off-by: Mark Salter<msalter@redhat.com> > --- > include/asm-generic/uaccess.h | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h > index ac68c99..1d0fdf8 100644 > --- a/include/asm-generic/uaccess.h > +++ b/include/asm-generic/uaccess.h > @@ -289,7 +289,7 @@ strncpy_from_user(char *dst, const char __user *src, long count) > * Return 0 on exception, a value greater than N if too long > */ > #ifndef __strnlen_user > -#define __strnlen_user strnlen > +#define __strnlen_user(s, n) (strnlen((s), (n)) + 1) > #endif
I don't think this is correct because if you hit maxlen you will add one to it. e.g. __strnlen_user("abcd\0", 3) would return 4 instead of 3.
It should probably be something like this:
#define __strnlen_user(s, n) ({ \ size_t k = strnlen(s, n); \ k< n ? k + 1 : n; })
I wonder if this change will break anything since it has been incorrect (according to the comment in uaccess.h at least) for a while. Why does __strnlen_user have different semantics to strnlen anway?
~Ryan
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