linux-stable.git/fs/proc/task_mmu.c, branch linux-3.10.y

mm: larger stack guard gap, between vmas

2017-06-21T13:42:43+00:00

commit 1be7107fbe18eed3e319a6c3e83c78254b693acb upstream.

Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.

Original-patch-by: Oleg Nesterov 
Original-patch-by: Michal Hocko 
Signed-off-by: Hugh Dickins 
[wt: backport to 4.11: adjust context]
[wt: backport to 4.9: adjust context ; kernel doc was not in admin-guide]
[wt: backport to 4.4: adjust context ; drop ppc hugetlb_radix changes]
[wt: backport to 3.18: adjust context ; no FOLL_POPULATE ;
     s390 uses generic arch_get_unmapped_area()]
[wt: backport to 3.16: adjust context]
[wt: backport to 3.10: adjust context ; code logic in PARISC's
     arch_get_unmapped_area() wasn't found ; code inserted into
     expand_upwards() and expand_downwards() runs under anon_vma lock;
     changes for gup.c:faultin_page go to memory.c:__get_user_pages();
     included Hugh Dickins' fixes]
Signed-off-by: Willy Tarreau

proc: Fix ptrace-based permission checks for accessing task maps

2016-03-03T23:06:19+00:00

Modify mm_access() calls in fs/proc/task_mmu.c and fs/proc/task_nommu.c to
have the mode include PTRACE_MODE_FSCREDS so accessing /proc/pid/maps and
/proc/pid/pagemap is not denied to all users.

In backporting upstream commit caaee623 to pre-3.18 kernel versions it was
overlooked that mm_access() is used in fs/proc/task_*mmu.c as those calls
were removed in 3.18 (by upstream commit 29a40ace) and did not exist at the
time of the original commit.

Signed-off-by: Corey Wright 
Acked-by: Jann Horn 
Signed-off-by: Greg Kroah-Hartman

pagemap: do not leak physical addresses to non-privileged userspace

2015-04-19T08:10:51+00:00

commit ab676b7d6fbf4b294bf198fb27ade5b0e865c7ce upstream.

As pointed by recent post[1] on exploiting DRAM physical imperfection,
/proc/PID/pagemap exposes sensitive information which can be used to do
attacks.

This disallows anybody without CAP_SYS_ADMIN to read the pagemap.

[1] http://googleprojectzero.blogspot.com/2015/03/exploiting-dram-rowhammer-bug-to-gain.html

[ Eventually we might want to do anything more finegrained, but for now
  this is the simple model.   - Linus ]

Signed-off-by: Kirill A. Shutemov 
Acked-by: Konstantin Khlebnikov 
Acked-by: Andy Lutomirski 
Cc: Pavel Emelyanov 
Cc: Andrew Morton 
Cc: Mark Seaborn 
Signed-off-by: Linus Torvalds 
Signed-off-by: mancha security 
Signed-off-by: Greg Kroah-Hartman

fs/proc/task_mmu.c: fix buffer overflow in add_page_map()

2013-08-20T15:43:02+00:00

commit 8c8296223f3abb142be8fc31711b18a704c0e7d8 upstream.

Recently we met quite a lot of random kernel panic issues after enabling
CONFIG_PROC_PAGE_MONITOR.  After debuggind we found this has something
to do with following bug in pagemap:

In struct pagemapread:

  struct pagemapread {
      int pos, len;
      pagemap_entry_t *buffer;
      bool v2;
  };

pos is number of PM_ENTRY_BYTES in buffer, but len is the size of
buffer, it is a mistake to compare pos and len in add_page_map() for
checking buffer is full or not, and this can lead to buffer overflow and
random kernel panic issue.

Correct len to be total number of PM_ENTRY_BYTES in buffer.

[akpm@linux-foundation.org: document pagemapread.pos and .len units, fix PM_ENTRY_BYTES definition]
Signed-off-by: Yonghua Zheng 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

new helper: file_inode(file)

2013-02-23T04:31:31+00:00

Signed-off-by: Al Viro

mempolicy: remove arg from mpol_parse_str, mpol_to_str

2013-01-02T17:27:10+00:00

Remove the unused argument (formerly no_context) from mpol_parse_str()
and from mpol_to_str().

Signed-off-by: Hugh Dickins 
Signed-off-by: Linus Torvalds

procfs: add VmFlags field in smaps output

2012-12-18T01:15:22+00:00

During c/r sessions we've found that there is no way at the moment to
fetch some VMA associated flags, such as mlock() and madvise().

This leads us to a problem -- we don't know if we should call for mlock()
and/or madvise() after restore on the vma area we're bringing back to
life.

This patch intorduces a new field into "smaps" output called VmFlags,
where all set flags associated with the particular VMA is shown as two
letter mnemonics.

[ Strictly speaking for c/r we only need mlock/madvise bits but it has been
  said that providing just a few flags looks somehow inconsistent.  So all
  flags are here now. ]

This feature is made available on CONFIG_CHECKPOINT_RESTORE=n kernels, as
other applications may start to use these fields.

The data is encoded in a somewhat awkward two letters mnemonic form, to
encourage userspace to be prepared for fields being added or removed in
the future.

[a.p.zijlstra@chello.nl: props to use for_each_set_bit]
[sfr@canb.auug.org.au: props to use array instead of struct]
[akpm@linux-foundation.org: overall redesign and simplification]
[akpm@linux-foundation.org: remove unneeded braces per sfr, avoid using bloaty for_each_set_bit()]
Signed-off-by: Cyrill Gorcunov 
Cc: Pavel Emelyanov 
Cc: Peter Zijlstra 
Cc: Stephen Rothwell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

procfs: use N_MEMORY instead N_HIGH_MEMORY

2012-12-13T01:38:32+00:00

N_HIGH_MEMORY stands for the nodes that has normal or high memory.
N_MEMORY stands for the nodes that has any memory.

The code here need to handle with the nodes which have memory, we should
use N_MEMORY instead.

Signed-off-by: Lai Jiangshan 
Acked-by: Hillf Danton 
Signed-off-by: Wen Congyang 
Cc: Christoph Lameter 
Cc: Lin Feng 
Cc: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

thp: change split_huge_page_pmd() interface

2012-12-13T01:38:31+00:00

Pass vma instead of mm and add address parameter.

In most cases we already have vma on the stack. We provides
split_huge_page_pmd_mm() for few cases when we have mm, but not vma.

This change is preparation to huge zero pmd splitting implementation.

Signed-off-by: Kirill A. Shutemov 
Cc: Andrea Arcangeli 
Cc: Andi Kleen 
Cc: "H. Peter Anvin" 
Cc: Mel Gorman 
Cc: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

hold task->mempolicy while numa_maps scans.

2012-10-19T21:32:10+00:00

  /proc//numa_maps scans vma and show mempolicy under
  mmap_sem. It sometimes accesses task->mempolicy which can
  be freed without mmap_sem and numa_maps can show some
  garbage while scanning.

This patch tries to take reference count of task->mempolicy at reading
numa_maps before calling get_vma_policy(). By this, task->mempolicy
will not be freed until numa_maps reaches its end.

V2->v3
  -  updated comments to be more verbose.
  -  removed task_lock() in numa_maps code.
V1->V2
  -  access task->mempolicy only once and remember it.  Becase kernel/exit.c
     can overwrite it.

Signed-off-by: KAMEZAWA Hiroyuki 
Acked-by: David Rientjes 
Acked-by: KOSAKI Motohiro 
Signed-off-by: Linus Torvalds