For security reasons, UML in is_syscall() needs to have access to code in
vsyscall-page. The current implementation grants this access by explicitly
allowing access to vsyscall in access_ok_skas(). With this change,
copy_from_user() may be used to read the code. Ptrace access to vsyscall-page
for debugging already was implemented in get_user_pages() by mainline. In
i386, copy_from_user can't access vsyscall-page, but returns EFAULT.
To make UML behave as i386 does, I changed is_syscall to use
access_process_vm(current) to read the code from vsyscall-page. This doesn't
hurt security, but simplifies the code and prepares implementation of
stub-vmas.
Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
81efcd3300