From d6bbbd29b1de2da807753be8a3a992a72aef42de Mon Sep 17 00:00:00 2001 From: Raymond Jennings Date: Wed, 11 Sep 2013 14:20:16 -0700 Subject: [PATCH] swap: warn when a swap area overflows the maximum size It is possible to swapon a swap area that is too big for the pte width to handle. Presently this failure happens silently. Instead, emit a diagnostic to warn the user. Testing results, root prompt commands and kernel log messages: # lvresize /dev/system/swap --size 16G # mkswap /dev/system/swap # swapon /dev/system/swap Jul 7 04:27:22 warfang kernel: Adding 16777212k swap on /dev/mapper/system-swap. Priority:-1 extents:1 across:16777212k # lvresize /dev/system/swap --size 64G # mkswap /dev/system/swap # swapon /dev/system/swap Jul 7 04:27:22 warfang kernel: Truncating oversized swap area, only using 33554432k out of 67108860k Jul 7 04:27:22 warfang kernel: Adding 33554428k swap on /dev/mapper/system-swap. Priority:-1 extents:1 across:33554428k [akpm@linux-foundation.org: fix warning] Signed-off-by: Raymond Jennings Acked-by: Valdis Kletnieks Reviewed-by: Rik van Riel Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swapfile.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 6cf2e60983b7..b5212eea6c3c 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1926,6 +1926,7 @@ static unsigned long read_swap_header(struct swap_info_struct *p, int i; unsigned long maxpages; unsigned long swapfilepages; + unsigned long last_page; if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { printk(KERN_ERR "Unable to find swap-space signature\n"); @@ -1968,8 +1969,15 @@ static unsigned long read_swap_header(struct swap_info_struct *p, */ maxpages = swp_offset(pte_to_swp_entry( swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; - if (maxpages > swap_header->info.last_page) { - maxpages = swap_header->info.last_page + 1; + last_page = swap_header->info.last_page; + if (last_page > maxpages) { + printk(KERN_WARNING + "Truncating oversized swap area, only using %luk out of %luk\n", + maxpages << (PAGE_SHIFT - 10), + last_page << (PAGE_SHIFT - 10)); + } + if (maxpages > last_page) { + maxpages = last_page + 1; /* p->max is an unsigned int: don't overflow it */ if ((unsigned int)maxpages == 0) maxpages = UINT_MAX;