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>
We have found that the current PER_CLEAR_ON_SETID mask on Linux doesn't
include neither ADDR_COMPAT_LAYOUT, nor MMAP_PAGE_ZERO.
The current mask is READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE.
We believe it is important to add MMAP_PAGE_ZERO, because by using this
personality it is possible to have the first page mapped inside a
process running as setuid root. This could be used in those scenarios:
- Exploiting a NULL pointer dereference issue in a setuid root binary
- Bypassing the mmap_min_addr restrictions of the Linux kernel: by
running a setuid binary that would drop privileges before giving us
control back (for instance by loading a user-supplied library), we
could get the first page mapped in a process we control. By further
using mremap and mprotect on this mapping, we can then completely
bypass the mmap_min_addr restrictions.
Less importantly, we believe ADDR_COMPAT_LAYOUT should also be added
since on x86 32bits it will in practice disable most of the address
space layout randomization (only the stack will remain randomized).
Signed-off-by: Julien Tinnes <jt@cr0.org>
Signed-off-by: Tavis Ormandy <taviso@sdf.lonestar.org>
Cc: stable@kernel.org
Acked-by: Christoph Hellwig <hch@infradead.org>
Acked-by: Kees Cook <kees@ubuntu.com>
Acked-by: Eugene Teo <eugene@redhat.com>
[ Shortened lines and fixed whitespace as per Christophs' suggestion ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If you call set_personality() with an expression such as:
set_personality(foo ? PERS_FOO1 : PERS_FOO2);
then this evaluates to:
((current->personality == foo ? PERS_FOO1 : PERS_FOO2) ? ...
which is obviously not the intended result. Add the missing parents
to ensure this gets evaluated as expected:
((current->personality == (foo ? PERS_FOO1 : PERS_FOO2)) ? ...
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
<linux/personality.h> contains the constants for personality(2) but also
some defintions that are useless or even harmful in userspace such as the
personality() macro.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Oleg Nesterov
Julien Tinnes
WANG Cong
Russell King
Ralf Baechle
Linus Torvalds