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Date: Sat, 2 May 2009 22:08:41 -0400 From: Rik van Riel <riel@...riel.com> To: Izik Eidus <ieidus@...hat.com> Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, aarcange@...hat.com, chrisw@...hat.com, alan@...rguk.ukuu.org.uk, device@...ana.org, linux-mm@...ck.org, hugh@...itas.com, nickpiggin@...oo.com.au, Izik Eidus <ieidus@...hat.com> Subject: Re: [PATCH 1/6] ksm: limiting the num of mem regions user can register per fd. On Sun, 3 May 2009 01:16:07 +0300 Izik Eidus <ieidus@...hat.com> wrote: > Right now user can open /dev/ksm fd and register unlimited number of > regions, such behavior may allocate unlimited amount of kernel memory > and get the whole host into out of memory situation. > > Signed-off-by: Izik Eidus <ieidus@...hat.com> > --- > mm/ksm.c | 15 +++++++++++++++ > 1 files changed, 15 insertions(+), 0 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index 6165276..d58db6b 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -48,6 +48,9 @@ static int rmap_hash_size; > module_param(rmap_hash_size, int, 0); > MODULE_PARM_DESC(rmap_hash_size, "Hash table size for the reverse > mapping"); > +static int regions_per_fd; > +module_param(regions_per_fd, int, 0); > + > /* > * ksm_mem_slot - hold information for an userspace scanning range > * (the scanning for this region will be from addr untill addr + > @@ -67,6 +70,7 @@ struct ksm_mem_slot { > */ > struct ksm_sma { > struct list_head sma_slots; > + int nregions; > }; > > /** > @@ -453,6 +457,11 @@ static int > ksm_sma_ioctl_register_memory_region(struct ksm_sma *ksm_sma, struct > ksm_mem_slot *slot; int ret = -EPERM; > > + if ((ksm_sma->nregions + 1) > regions_per_fd) { > + ret = -EBUSY; > + goto out; > + } > + > slot = kzalloc(sizeof(struct ksm_mem_slot), GFP_KERNEL); > if (!slot) { > ret = -ENOMEM; > @@ -473,6 +482,7 @@ static int > ksm_sma_ioctl_register_memory_region(struct ksm_sma *ksm_sma, > list_add_tail(&slot->link, &slots); > list_add_tail(&slot->sma_link, &ksm_sma->sma_slots); > + ksm_sma->nregions++; > > up_write(&slots_lock); > return 0; > @@ -511,6 +521,7 @@ static int > ksm_sma_ioctl_remove_memory_region(struct ksm_sma *ksm_sma) > mmput(slot->mm); list_del(&slot->sma_link); > kfree(slot); > + ksm_sma->nregions--; > } > up_write(&slots_lock); > return 0; > @@ -1389,6 +1400,7 @@ static int > ksm_dev_ioctl_create_shared_memory_area(void) } > > INIT_LIST_HEAD(&ksm_sma->sma_slots); > + ksm_sma->nregions = 0; > > fd = anon_inode_getfd("ksm-sma", &ksm_sma_fops, ksm_sma, 0); > if (fd < 0) > @@ -1631,6 +1643,9 @@ static int __init ksm_init(void) > if (r) > goto out_free1; > > + if (!regions_per_fd) > + regions_per_fd = 1024; > + > ksm_thread = kthread_run(ksm_scan_thread, NULL, "kksmd"); > if (IS_ERR(ksm_thread)) { > printk(KERN_ERR "ksm: creating kthread failed\n"); -- All rights reversed. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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