From: Vlastimil Babka Date: Thu, 10 Nov 2016 18:46:07 +0000 (-0800) Subject: mm, frontswap: make sure allocated frontswap map is assigned X-Git-Tag: v4.9-rc5~20^2~13 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=5e322beefc8699b5747cfb35539a9496034e4296;p=karo-tx-linux.git mm, frontswap: make sure allocated frontswap map is assigned Christian Borntraeger reports: With commit 8ea1d2a1985a ("mm, frontswap: convert frontswap_enabled to static key") kmemleak complains about a memory leak in swapon unreferenced object 0x3e09ba56000 (size 32112640): comm "swapon", pid 7852, jiffies 4294968787 (age 1490.770s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: __vmalloc_node_range+0x194/0x2d8 vzalloc+0x58/0x68 SyS_swapon+0xd60/0x12f8 system_call+0xd6/0x270 Turns out kmemleak is right. We now allocate the frontswap map depending on the kernel config (and no longer on the enablement) swapfile.c: [...] if (IS_ENABLED(CONFIG_FRONTSWAP)) frontswap_map = vzalloc(BITS_TO_LONGS(maxpages) * sizeof(long)); but later on this is passed along --> enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map); and ignored if frontswap is disabled --> frontswap_init(p->type, frontswap_map); static inline void frontswap_init(unsigned type, unsigned long *map) { if (frontswap_enabled()) __frontswap_init(type, map); } Thing is, that frontswap map is never freed. The leakage is relatively not that bad, because swapon is an infrequent and privileged operation. However, if the first frontswap backend is registered after a swap type has been already enabled, it will WARN_ON in frontswap_register_ops() and frontswap will not be available for the swap type. Fix this by making sure the map is assigned by frontswap_init() as long as CONFIG_FRONTSWAP is enabled. Fixes: 8ea1d2a1985a ("mm, frontswap: convert frontswap_enabled to static key") Link: http://lkml.kernel.org/r/20161026134220.2566-1-vbabka@suse.cz Signed-off-by: Vlastimil Babka Reported-by: Christian Borntraeger Cc: Konrad Rzeszutek Wilk Cc: Boris Ostrovsky Cc: David Vrabel Cc: Juergen Gross Cc: "Kirill A. Shutemov" Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h index c46d2aa16d81..1d18af034554 100644 --- a/include/linux/frontswap.h +++ b/include/linux/frontswap.h @@ -106,8 +106,9 @@ static inline void frontswap_invalidate_area(unsigned type) static inline void frontswap_init(unsigned type, unsigned long *map) { - if (frontswap_enabled()) - __frontswap_init(type, map); +#ifdef CONFIG_FRONTSWAP + __frontswap_init(type, map); +#endif } #endif /* _LINUX_FRONTSWAP_H */