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SubjectRe: filldir[64] oddness
On Wed, Mar 08, 2006 at 11:27:44PM -0500, Dave Jones wrote:
> I'm puzzled by an aparent use of uninitialised memory
> that coverity's checker picked up.
>
> fs/readdir.c
>
> #define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
> #define ROUND_UP(x) (((x)+sizeof(long)-1) & ~(sizeof(long)-1))
>
> 140 static int filldir(void * __buf, const char * name, int namlen, loff_t offset,
> 141 ino_t ino, unsigned int d_type)
> 142 {
> 143 struct linux_dirent __user * dirent;
> 144 struct getdents_callback * buf = (struct getdents_callback *) __buf
> 145 int reclen = ROUND_UP(NAME_OFFSET(dirent) + namlen + 2);
>
> How come that NAME_OFFSET isn't causing an oops when
> it dereferences stackjunk->d_name ?

It doesn't dereference it. d_name is an array, not a pointer. FWIW,
it should've been

#define NAME_OFFSET(de) offsetof(typeof(de), d_name)

or, better yet

#define NAME_OFFSET offsetof(struct linux_dirent, d_name)
#define NAME_OFFSET64 offsetof(struct linux_dirent64, d_name)
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