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mm: mempolicy: require at least one nodeid for MPOL_PREFERRED

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Using an empty (malformed) nodelist that is not caught during mount option
parsing leads to a stack-out-of-bounds access.

The option string that was used was: "mpol=prefer:,".  However,
MPOL_PREFERRED requires a single node number, which is not being provided
here.

Add a check that 'nodes' is not empty after parsing for MPOL_PREFERRED's
nodeid.

Fixes: 095f1fc4eb ("mempolicy: rework shmem mpol parsing and display")
Reported-by: Entropy Moe <3ntr0py1337@gmail.com>
Reported-by: syzbot+b055b1a6b2b958707a21@syzkaller.appspotmail.com
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: syzbot+b055b1a6b2b958707a21@syzkaller.appspotmail.com
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Link: http://lkml.kernel.org/r/89526377-7eb6-b662-e1d8-4430928abde9@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Randy Dunlap 2020-04-01 21:10:58 -07:00 committed by Linus Torvalds
parent d888fb2b18
commit aa9f7d5172
1 changed files with 5 additions and 1 deletions
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6
mm/mempolicy.c
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@ -2898,7 +2898,9 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
switch (mode) {
case MPOL_PREFERRED:
/*
* Insist on a nodelist of one node only
* Insist on a nodelist of one node only, although later
* we use first_node(nodes) to grab a single node, so here
* nodelist (or nodes) cannot be empty.
*/
if (nodelist) {
char *rest = nodelist;
@ -2906,6 +2908,8 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
rest++;
if (*rest)
goto out;
if (nodes_empty(nodes))
goto out;
}
break;
case MPOL_INTERLEAVE: