Commit 56521e7a authored Jan 31, 2018 by Yisheng Xie Committed by Linus Torvalds Jan 31, 2018

mm/mempolicy: fix the check of nodemask from user

As Xiaojun reported the ltp of migrate_pages01 will fail on arm64 system
which has 4 nodes[0...3], all have memory and CONFIG_NODES_SHIFT=2:

  migrate_pages01    0  TINFO  :  test_invalid_nodes
  migrate_pages01   14  TFAIL  :  migrate_pages_common.c:45: unexpected failure - returned value = 0, expected: -1
  migrate_pages01   15  TFAIL  :  migrate_pages_common.c:55: call succeeded unexpectedly

In this case the test_invalid_nodes of migrate_pages01 will call:
SYSC_migrate_pages as:

  migrate_pages(0, , {0x0000000000000001}, 64, , {0x0000000000000010}, 64) = 0

The new nodes specifies one or more node IDs that are greater than the
maximum supported node ID, however, the errno is not set to EINVAL as
expected.

As man pages of set_mempolicy[1], mbind[2], and migrate_pages[3]
mentioned, when nodemask specifies one or more node IDs that are greater
than the maximum supported node ID, the errno should set to EINVAL.
However, get_nodes only check whether the part of bits
[BITS_PER_LONG*BITS_TO_LONGS(MAX_NUMNODES), maxnode) is zero or not, and
remain [MAX_NUMNODES, BITS_PER_LONG*BITS_TO_LONGS(MAX_NUMNODES)
unchecked.

This patch is to check the bits of [MAX_NUMNODES, maxnode) in get_nodes
to let migrate_pages set the errno to EINVAL when nodemask specifies one
or more node IDs that are greater than the maximum supported node ID,
which follows the manpage's guide.

[1] http://man7.org/linux/man-pages/man2/set_mempolicy.2.html
[2] http://man7.org/linux/man-pages/man2/mbind.2.html
[3] http://man7.org/linux/man-pages/man2/migrate_pages.2.html

Link: http://lkml.kernel.org/r/1510882624-44342-3-git-send-email-xieyisheng1@huawei.com


Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Reported-by: Tan Xiaojun <tanxiaojun@huawei.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Chris Salls <salls@cs.ucsb.edu>
Cc: Christopher Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 66f308ed

mm/mempolicy.c

+20 −3

Original line number	Diff line number	Diff line
		@@ -1263,6 +1263,7 @@ static int get_nodes(nodemask_t nodes, const unsigned long __user nmask,
		unsigned long maxnode)
		{
		unsigned long k;
		unsigned long t;
		unsigned long nlongs;
		unsigned long endmask;

		@@ -1279,11 +1280,17 @@ static int get_nodes(nodemask_t nodes, const unsigned long __user nmask,
		else
		endmask = (1UL << (maxnode % BITS_PER_LONG)) - 1;

		/* When the user specified more nodes than supported just check
		if the non supported part is all zero. */
		/*
		* When the user specified more nodes than supported just check
		* if the non supported part is all zero.
		*
		* If maxnode have more longs than MAX_NUMNODES, check
		* the bits in that area first. And then go through to
		* check the rest bits which equal or bigger than MAX_NUMNODES.
		* Otherwise, just check bits [MAX_NUMNODES, maxnode).
		*/
		if (nlongs > BITS_TO_LONGS(MAX_NUMNODES)) {
		for (k = BITS_TO_LONGS(MAX_NUMNODES); k < nlongs; k++) {
		unsigned long t;
		if (get_user(t, nmask + k))
		return -EFAULT;
		if (k == nlongs - 1) {
		@@ -1296,6 +1303,16 @@ static int get_nodes(nodemask_t nodes, const unsigned long __user nmask,
		endmask = ~0UL;
		}

		if (maxnode > MAX_NUMNODES && MAX_NUMNODES % BITS_PER_LONG != 0) {
		unsigned long valid_mask = endmask;

		valid_mask &= ~((1UL << (MAX_NUMNODES % BITS_PER_LONG)) - 1);
		if (get_user(t, nmask + nlongs - 1))
		return -EFAULT;
		if (t & valid_mask)
		return -EINVAL;
		}

		if (copy_from_user(nodes_addr(nodes), nmask, nlongssizeof(unsigned long)))
		return -EFAULT;
		nodes_addr(*nodes)[nlongs-1] &= endmask;

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