From da8c757b080ee84f219fa2368cb5dd23ac304fc0 Mon Sep 17 00:00:00 2001 From: Han Pingtian Date: Thu, 23 Jan 2014 15:53:17 -0800 Subject: 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 6fce56ec91b5 ("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 Acked-by: Michal Hocko Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f18f016..a818d56 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -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(); -- cgit v0.10.2