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From: Li Xinhai <lixinhai.lxh@gmail.com>
To: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>,
	Hugh Dickins <hughd@google.com>
Subject: [PATCH] mm: mempolicy: Fix wrong use of maxnode in mempolicy API
Date: Fri,  8 Nov 2019 23:49:29 +0800	[thread overview]
Message-ID: <1573228169-30986-1-git-send-email-lixinhai.lxh@gmail.com> (raw)

The maxnode used by mbind(), set_mempolicy() and migrate_pages() is not
correctly handled in get_nodes(), where --maxnode cause the calculation
  endmask = (1UL << (maxnode % BITS_PER_LONG)) - 1;
ignores the highest node ID bit. Then, at
  nodes_addr(*nodes)[nlongs-1] &= endmask;
the highest node ID bit is cleared. Finally, cause mpol_new() think user
does not pass in any node ID, and return EINVAL.

The results are:
- Application receives EINVAL when only the highest node ID bit is set.
- Application recevies no error when other bits set together with the
  highest node ID bit, but that highest ID is ignored.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com>
---
 mm/mempolicy.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 4ae967b..2bdc365 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1328,7 +1328,6 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
 	unsigned long nlongs;
 	unsigned long endmask;
 
-	--maxnode;
 	nodes_clear(*nodes);
 	if (maxnode == 0 || !nmask)
 		return 0;
-- 
1.8.3.1



             reply	other threads:[~2019-11-08 15:50 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08 15:49 Li Xinhai [this message]
2019-11-08 16:04 ` [PATCH] mm: mempolicy: Fix wrong use of maxnode in mempolicy API Michal Hocko
2019-11-08 16:48   ` lixinhai.lxh
2019-11-11 10:04     ` Michal Hocko

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