sys_personality: change sys_personality() to accept "unsigned int" instead of u_long

task_struct->pesonality is "unsigned int", but sys_personality() paths use
"unsigned long pesonality".  This means that every assignment or
comparison is not right.  In particular, if this argument does not fit
into "unsigned int" __set_personality() changes the caller's personality
and then sys_personality() returns -EINVAL.

Turn this argument into "unsigned int" and avoid overflows.  Obviously,
this is the user-visible change, we just ignore the upper bits.  But this
can't break the sane application.

There is another thing which can confuse the poorly written applications.
User-space thinks that this syscall returns int, not long.  This means
that the returned value can be negative and look like the error code.  But
note that libc won't be confused and thus errno won't be set, and with
this patch the user-space can never get -1 unless sys_personality() really
fails.  And, most importantly, the negative RET != -1 is only possible if
that app previously called personality(RET).

Pointed-out-by: Wenming Zhang <wezhang@redhat.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/personality.h b/include/linux/personality.h
index 126120819a0d..eec3bae164d4 100644
--- a/include/linux/personality.h
+++ b/include/linux/personality.h
@@ -12,7 +12,7 @@ struct pt_regs;
 
 extern int              register_exec_domain(struct exec_domain *);
 extern int              unregister_exec_domain(struct exec_domain *);
-extern int              __set_personality(unsigned long);
+extern int              __set_personality(unsigned int);
 
 #endif /* __KERNEL__ */
 
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index a1a86a53bc73..7f614ce274a9 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -289,7 +289,7 @@ asmlinkage long sys_capget(cap_user_header_t header,
                                 cap_user_data_t dataptr);
 asmlinkage long sys_capset(cap_user_header_t header,
                                 const cap_user_data_t data);
-asmlinkage long sys_personality(u_long personality);
+asmlinkage long sys_personality(unsigned int personality);
 
 asmlinkage long sys_sigpending(old_sigset_t __user *set);
 asmlinkage long sys_sigprocmask(int how, old_sigset_t __user *set,