linux.git/fs/binfmt_elf.c, branch v2.6.32

elf: clean up fill_note_info()

2009-09-24T14:21:01+00:00

Introduce a helper function elf_note_info_init() to help fill_note_info()
to do initializations, also fix the potential memory leaks.

[akpm@linux-foundation.org: remove NUM_NOTES]
Signed-off-by: WANG Cong 
Cc: Alexander Viro 
Cc: David Howells 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: add get_dump_page

2009-09-22T14:17:40+00:00

In preparation for the next patch, add a simple get_dump_page(addr)
interface for the CONFIG_ELF_CORE dumpers to use, instead of calling
get_user_pages() directly.  They're not interested in errors: they
just want to use holes as much as possible, to save space and make
sure that the data is aligned where the headers said it would be.

Oh, and don't use that horrid DUMP_SEEK(off) macro!

Signed-off-by: Hugh Dickins 
Acked-by: Rik van Riel 
Cc: KAMEZAWA Hiroyuki 
Cc: KOSAKI Motohiro 
Cc: Nick Piggin 
Cc: Mel Gorman 
Cc: Minchan Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

binfmt_elf: fix PT_INTERP bss handling

2009-09-10T03:03:47+00:00

In fs/binfmt_elf.c, load_elf_interp() calls padzero() for .bss even if
the PT_LOAD has no PROT_WRITE and no .bss.  This generates EFAULT.

Here is a small test case.  (Yes, there are other, useful PT_INTERP
which have only .text and no .data/.bss.)

	----- ptinterp.S
	_start: .globl _start
		 nop
		 int3
	-----
	$ gcc -m32 -nostartfiles -nostdlib -o ptinterp ptinterp.S
	$ gcc -m32 -Wl,--dynamic-linker=ptinterp -o hello hello.c
	$ ./hello
	Segmentation fault  # during execve() itself

	After applying the patch:
	$ ./hello
	Trace trap  # user-mode execution after execve() finishes

If the ELF headers are actually self-inconsistent, then dying is fine.
But having no PROT_WRITE segment is perfectly normal and correct if
there is no segment with p_memsz > p_filesz (i.e. bss).  John Reiser
suggested checking for PROT_WRITE in the bss logic.  I think it makes
most sense to simply apply the bss logic only when there is bss.

This patch looks less trivial than it is due to some reindentation.
It just moves the "if (last_bss > elf_bss) {" test up to include the
partial-page bss logic as well as the more-pages bss logic.

Reported-by: John Reiser 
Signed-off-by: Roland McGrath 
Signed-off-by: Linus Torvalds

elf: fix one check-after-use

2009-07-01T18:14:28+00:00

Check before use it.

Signed-off-by: WANG Cong 
Cc: Alexander Viro 
Cc: David Howells 
Acked-by: Roland McGrath 
Acked-by: James Morris 
Signed-off-by: Linus Torvalds

elf: limit max map count to safe value

2009-07-01T01:55:59+00:00

With ELF, at generating coredump, some more headers other than used
vmas are added.

When max_map_count == 65536, a core generated by following kinds of
code can be unreadable because the number of ELF's program header is
written in 16bit in Ehdr (please see elf.h) and the number overflows.

==
	... = mmap(); (munmap, mprotect, etc...)
	if (failed)
		abort();
==

This can happen in mmap/munmap/mprotect/etc...which calls split_vma().

I think 65536 is not safe as _default_ and reduce it to 65530 is good
for avoiding unexpected corrupted core.

Anyway, max_map_count can be enlarged by sysctl if a user is brave..

Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Hugh Dickins 
Cc: Jakub Jelinek 
Acked-by: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

elf_core_dump: use rcu_read_lock() to access ->real_parent

2009-06-18T20:03:52+00:00

In theory it is not safe to dereference ->parent/real_parent without
tasklist or rcu lock, we can race with re-parenting.

Signed-off-by: Oleg Nesterov 
Acked-by: Roland McGrath 
Cc: David Howells 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Trim includes in binfmt_elf

2009-04-01T03:00:27+00:00

Signed-off-by: Al Viro

Don't mess with descriptor table in load_elf_binary()

2009-04-01T03:00:27+00:00

... since we don't tell anyone which descriptor does the file get.
We used to, but only in case of ELF binary with a.out loader and
that stuff has been gone for a while.

Signed-off-by: Al Viro

elf core dump: fix get_user use

2009-02-07T01:34:07+00:00

The elf_core_dump() code does its work with set_fs(KERNEL_DS) in force,
so vma_dump_size() needs to switch back with set_fs(USER_DS) to safely
use get_user() for a normal user-space address.

Checking for VM_READ optimizes out the case where get_user() would fail
anyway.  The vm_file check here was already superfluous given the control
flow earlier in the function, so that is a cleanup/optimization unrelated
to other changes but an obvious and trivial one.

Reported-by: Gerald Schaefer 
Signed-off-by: Roland McGrath

ELF: implement AT_RANDOM for glibc PRNG seeding

2009-01-08T16:31:12+00:00

While discussing[1] the need for glibc to have access to random bytes
during program load, it seems that an earlier attempt to implement
AT_RANDOM got stalled.  This implements a random 16 byte string, available
to every ELF program via a new auxv AT_RANDOM vector.

[1] http://sourceware.org/ml/libc-alpha/2008-10/msg00006.html

Ulrich said:

glibc needs right after startup a bit of random data for internal
protections (stack canary etc).  What is now in upstream glibc is that we
always unconditionally open /dev/urandom, read some data, and use it.  For
every process startup.  That's slow.

...

The solution is to provide a limited amount of random data to the
starting process in the aux vector.  I suggested 16 bytes and this is
what the patch implements.  If we need only 16 bytes or less we use the
data directly.  If we need more we'll use the 16 bytes to see a PRNG.
This avoids the costly /dev/urandom use and it allows the kernel to use
the most adequate source of random data for this purpose.  It might not
be the same pool as that for /dev/urandom.

Concerns were expressed about the depletion of the randomness pool.  But
this patch doesn't make the situation worse, it doesn't deplete entropy
more than happens now.

Signed-off-by: Kees Cook 
Cc: Jakub Jelinek 
Cc: Andi Kleen 
Cc: Ulrich Drepper 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds