Commit da8c757b authored Jan 23, 2014 by Han Pingtian Committed by Linus Torvalds Jan 23, 2014

mm: prevent setting of a value less than 0 to min_free_kbytes



If echo -1 > /proc/vm/sys/min_free_kbytes, the system will hang.  Changing
proc_dointvec() to proc_dointvec_minmax() in the
min_free_kbytes_sysctl_handler() can prevent this to happen.

mhocko said:

: You can still do echo $BIG_VALUE > /proc/vm/sys/min_free_kbytes and make
: your machine unusable but I agree that proc_dointvec_minmax is more
: suitable here as we already have:
:
: 	.proc_handler   = min_free_kbytes_sysctl_handler,
: 	.extra1         = &zero,
:
: It used to work properly but then 6fce56ec ("sysctl: Remove references
: to ctl_name and strategy from the generic sysctl table") has removed
: sysctl_intvec strategy and so extra1 is ignored.

Signed-off-by: Han Pingtian <hanpt@linux.vnet.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent cc81717e

mm/page_alloc.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -5754,7 +5754,12 @@ module_init(init_per_zone_wmark_min)
		int min_free_kbytes_sysctl_handler(ctl_table *table, int write,
		void __user buffer, size_t length, loff_t *ppos)
		{
		proc_dointvec(table, write, buffer, length, ppos);
		int rc;

		rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
		if (rc)
		return rc;

		if (write) {
		user_min_free_kbytes = min_free_kbytes;
		setup_per_zone_wmarks();

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