Messages in this thread | | | Date | Wed, 29 Mar 2023 17:15:16 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok |
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Hmm. I am not comfortable with this change...
I won't really argue because I don't have a better solution and because I think we don't really care as long as task_set_syscall_user_dispatch() is the only user of task_access_ok(), but still...
OK, so this version changes set_syscall_user_dispatch() to use task_access_ok() instead of access_ok() because task != current.
On 03/28, Gregory Price wrote: > > If the architecture does not implement task_access_ok, the operation > reduces to access_ok and the task argument is discarded.
No, with this patch it reduces to __access_ok(). And this already doesn't look very good to me, but this is minor.
> --- a/include/asm-generic/access_ok.h > +++ b/include/asm-generic/access_ok.h > @@ -45,4 +45,14 @@ static inline int __access_ok(const void __user *ptr, unsigned long size) > #define access_ok(addr, size) likely(__access_ok(addr, size)) > #endif > > +/* > + * Some architectures may have special features (such as ARM MTE) > + * that require handling if access_ok is called on a pointer from one > + * task in the context of another. On most architectures this operation > + * is equivalent to simply __access_ok. > + */ > +#ifndef task_access_ok > +#define task_access_ok(task, addr, size) likely(__access_ok(addr, size)) > +#endif
Lets ignore arm64.
This look as if access_ok() or __access_ok() doesn't depend on task, but this is not true in general. Say, TASK_SIZE_MAX can check is_32bit_task() test_thread_flag(TIF_32BIT...) and this uses "current".
Again, we probably do not care, but I don't like the fact task_access_ok() looks as if task_access_ok(task) returns the same result as "task" calling access_ok().
Oleg.
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