linux-toradex.git/fs/exec.c, branch v2.6.36.4

install_special_mapping skips security_file_mmap check.

2011-01-07T21:58:35+00:00

commit 462e635e5b73ba9a4c03913b77138cd57ce4b050 upstream.

The install_special_mapping routine (used, for example, to setup the
vdso) skips the security check before insert_vm_struct, allowing a local
attacker to bypass the mmap_min_addr security restriction by limiting
the available pages for special mappings.

bprm_mm_init() also skips the check, and although I don't think this can
be used to bypass any restrictions, I don't see any reason not to have
the security check.

  $ uname -m
  x86_64
  $ cat /proc/sys/vm/mmap_min_addr
  65536
  $ cat install_special_mapping.s
  section .bss
      resb BSS_SIZE
  section .text
      global _start
      _start:
          mov     eax, __NR_pause
          int     0x80
  $ nasm -D__NR_pause=29 -DBSS_SIZE=0xfffed000 -f elf -o install_special_mapping.o install_special_mapping.s
  $ ld -m elf_i386 -Ttext=0x10000 -Tbss=0x11000 -o install_special_mapping install_special_mapping.o
  $ ./install_special_mapping &
  [1] 14303
  $ cat /proc/14303/maps
  0000f000-00010000 r-xp 00000000 00:00 0                                  [vdso]
  00010000-00011000 r-xp 00001000 00:19 2453665                            /home/taviso/install_special_mapping
  00011000-ffffe000 rwxp 00000000 00:00 0                                  [stack]

It's worth noting that Red Hat are shipping with mmap_min_addr set to
4096.

Signed-off-by: Tavis Ormandy 
Acked-by: Kees Cook 
Acked-by: Robert Swiecki 
[ Changed to not drop the error code - akpm ]
Reviewed-by: James Morris 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

exec: copy-and-paste the fixes into compat_do_execve() paths

2010-12-09T21:32:57+00:00

commit 114279be2120a916e8a04feeb2ac976a10016f2f upstream.

Note: this patch targets 2.6.37 and tries to be as simple as possible.
That is why it adds more copy-and-paste horror into fs/compat.c and
uglifies fs/exec.c, this will be cleanuped later.

compat_copy_strings() plays with bprm->vma/mm directly and thus has
two problems: it lacks the RLIMIT_STACK check and argv/envp memory
is not visible to oom killer.

Export acct_arg_size() and get_arg_page(), change compat_copy_strings()
to use get_arg_page(), change compat_do_execve() to do acct_arg_size(0)
as do_execve() does.

Add the fatal_signal_pending/cond_resched checks into compat_count() and
compat_copy_strings(), this matches the code in fs/exec.c and certainly
makes sense.

Signed-off-by: Oleg Nesterov 
Cc: KOSAKI Motohiro 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

exec: make argv/envp memory visible to oom-killer

2010-12-09T21:32:57+00:00

commit 3c77f845722158206a7209c45ccddc264d19319c upstream.

Brad Spengler published a local memory-allocation DoS that
evades the OOM-killer (though not the virtual memory RLIMIT):
http://www.grsecurity.net/~spender/64bit_dos.c

execve()->copy_strings() can allocate a lot of memory, but
this is not visible to oom-killer, nobody can see the nascent
bprm->mm and take it into account.

With this patch get_arg_page() increments current's MM_ANONPAGES
counter every time we allocate the new page for argv/envp. When
do_execve() succeds or fails, we change this counter back.

Technically this is not 100% correct, we can't know if the new
page is swapped out and turn MM_ANONPAGES into MM_SWAPENTS, but
I don't think this really matters and everything becomes correct
once exec changes ->mm or fails.

Reported-by: Brad Spengler 
Reviewed-and-discussed-by: KOSAKI Motohiro 
Signed-off-by: Oleg Nesterov 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

Export dump_{write,seek} to binary loader modules

2010-10-15T02:15:28+00:00

If you build aout support as a module, you'll want these exported.

Reported-by: Tetsuo Handa 
Signed-off-by: Linus Torvalds

Un-inline the core-dump helper functions

2010-10-14T21:32:06+00:00

Tony Luck reports that the addition of the access_ok() check in commit
0eead9ab41da ("Don't dump task struct in a.out core-dumps") broke the
ia64 compile due to missing the necessary header file includes.

Rather than add yet another include () to make everything
happy, just uninline the silly core dump helper functions and move the
bodies to fs/exec.c where they make a lot more sense.

dump_seek() in particular was too big to be an inline function anyway,
and none of them are in any way performance-critical.  And we really
don't need to mess up our include file headers more than they already
are.

Reported-and-tested-by: Tony Luck 
Signed-off-by: Linus Torvalds

execve: make responsive to SIGKILL with large arguments

2010-09-10T15:10:26+00:00

An execve with a very large total of argument/environment strings
can take a really long time in the execve system call.  It runs
uninterruptibly to count and copy all the strings.  This change
makes it abort the exec quickly if sent a SIGKILL.

Note that this is the conservative change, to interrupt only for
SIGKILL, by using fatal_signal_pending().  It would be perfectly
correct semantics to let any signal interrupt the string-copying in
execve, i.e. use signal_pending() instead of fatal_signal_pending().
We'll save that change for later, since it could have user-visible
consequences, such as having a timer set too quickly make it so that
an execve can never complete, though it always happened to work before.

Signed-off-by: Roland McGrath 
Reviewed-by: KOSAKI Motohiro 
Signed-off-by: Linus Torvalds

execve: improve interactivity with large arguments

2010-09-10T15:10:26+00:00

This adds a preemption point during the copying of the argument and
environment strings for execve, in copy_strings().  There is already
a preemption point in the count() loop, so this doesn't add any new
points in the abstract sense.

When the total argument+environment strings are very large, the time
spent copying them can be much more than a normal user time slice.
So this change improves the interactivity of the rest of the system
when one process is doing an execve with very large arguments.

Signed-off-by: Roland McGrath 
Reviewed-by: KOSAKI Motohiro 
Signed-off-by: Linus Torvalds

setup_arg_pages: diagnose excessive argument size

2010-09-10T15:10:26+00:00

The CONFIG_STACK_GROWSDOWN variant of setup_arg_pages() does not
check the size of the argument/environment area on the stack.
When it is unworkably large, shift_arg_pages() hits its BUG_ON.
This is exploitable with a very large RLIMIT_STACK limit, to
create a crash pretty easily.

Check that the initial stack is not too large to make it possible
to map in any executable.  We're not checking that the actual
executable (or intepreter, for binfmt_elf) will fit.  So those
mappings might clobber part of the initial stack mapping.  But
that is just userland lossage that userland made happen, not a
kernel problem.

Signed-off-by: Roland McGrath 
Reviewed-by: KOSAKI Motohiro 
Signed-off-by: Linus Torvalds

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6

2010-08-18T16:35:08+00:00

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
  fs: brlock vfsmount_lock
  fs: scale files_lock
  lglock: introduce special lglock and brlock spin locks
  tty: fix fu_list abuse
  fs: cleanup files_lock locking
  fs: remove extra lookup in __lookup_hash
  fs: fs_struct rwlock to spinlock
  apparmor: use task path helpers
  fs: dentry allocation consolidation
  fs: fix do_lookup false negative
  mbcache: Limit the maximum number of cache entries
  hostfs ->follow_link() braino
  hostfs: dumb (and usually harmless) tpyo - strncpy instead of strlcpy
  remove SWRITE* I/O types
  kill BH_Ordered flag
  vfs: update ctime when changing the file's permission by setfacl
  cramfs: only unlock new inodes
  fix reiserfs_evict_inode end_writeback second call

fs: fs_struct rwlock to spinlock

2010-08-18T12:35:46+00:00

fs: fs_struct rwlock to spinlock

struct fs_struct.lock is an rwlock with the read-side used to protect root and
pwd members while taking references to them. Taking a reference to a path
typically requires just 2 atomic ops, so the critical section is very small.
Parallel read-side operations would have cacheline contention on the lock, the
dentry, and the vfsmount cachelines, so the rwlock is unlikely to ever give a
real parallelism increase.

Replace it with a spinlock to avoid one or two atomic operations in typical
path lookup fastpath.

Signed-off-by: Nick Piggin 
Signed-off-by: Al Viro