Ritesh Harjani 4eff80b140 iomap: Fix negative assignment to unsigned sis->pages in iomap_swapfile_activate ... [ Upstream commit 5808fecc572391867fcd929662b29c12e6d08d81 ] In case if isi.nr_pages is 0, we are making sis->pages (which is unsigned int) a huge value in iomap_swapfile_activate() by assigning -1. This could cause a kernel crash in kernel v4.18 (with below signature). Or could lead to unknown issues on latest kernel if the fake big swap gets used. Fix this issue by returning -EINVAL in case of nr_pages is 0, since it is anyway a invalid swapfile. Looks like this issue will be hit when we have pagesize < blocksize type of configuration. I was able to hit the issue in case of a tiny swap file with below test script. https://raw.githubusercontent.com/riteshharjani/LinuxStudy/master/scripts/swap-issue.sh kernel crash analysis on v4.18 ============================== On v4.18 kernel, it causes a kernel panic, since sis->pages becomes a huge value and isi.nr_extents is 0. When 0 is returned it is considered as a swapfile over NFS and SWP_FILE is set (sis->flags |= SWP_FILE). Then when swapoff was getting called it was calling a_ops->swap_deactivate() if (sis->flags & SWP_FILE) is true. Since a_ops->swap_deactivate() is NULL in case of XFS, it causes below panic. Panic signature on v4.18 kernel: ======================================= root@qemu:/home/qemu# [ 8291.723351] XFS (loop2): Unmounting Filesystem [ 8292.123104] XFS (loop2): Mounting V5 Filesystem [ 8292.132451] XFS (loop2): Ending clean mount [ 8292.263362] Adding 4294967232k swap on /mnt1/test/swapfile. Priority:-2 extents:1 across:274877906880k [ 8292.277834] Unable to handle kernel paging request for instruction fetch [ 8292.278677] Faulting instruction address: 0x00000000 cpu 0x19: Vector: 400 (Instruction Access) at [c0000009dd5b7ad0] pc: 0000000000000000 lr: c0000000003eb9dc: destroy_swap_extents+0xfc/0x120 sp: c0000009dd5b7d50 msr: 8000000040009033 current = 0xc0000009b6710080 paca = 0xc00000003ffcb280 irqmask: 0x03 irq_happened: 0x01 pid = 5604, comm = swapoff Linux version 4.18.0 (riteshh@xxxxxxx) (gcc version 8.4.0 (Ubuntu 8.4.0-1ubuntu1~18.04)) #57 SMP Wed Mar 3 01:33:04 CST 2021 enter ? for help [link register ] c0000000003eb9dc destroy_swap_extents+0xfc/0x120 [c0000009dd5b7d50] c0000000025a7058 proc_poll_event+0x0/0x4 (unreliable) [c0000009dd5b7da0] c0000000003f0498 sys_swapoff+0x3f8/0x910 [c0000009dd5b7e30] c00000000000bbe4 system_call+0x5c/0x70 Exception: c01 (System Call) at 00007ffff7d208d8 Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com> [djwong: rework the comment to provide more details] Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Sasha Levin <sashal@kernel.org>		2021-04-07 15:00:04 +02:00
..
apply.c	iomap: Make sure iomap_end is called after iomap_begin	2020-07-06 10:49:27 -07:00
buffered-io.c	iomap: clean up writeback state logic on writepage error	2020-11-04 08:52:46 -08:00
direct-io.c	iomap: Call inode_dio_end() before generic_write_sync()	2020-09-28 08:51:08 -07:00
fiemap.c	fs: handle FIEMAP_FLAG_SYNC in fiemap_prep	2020-06-03 23:16:55 -04:00
Makefile	iomap: lift common tracing code from xfs to iomap	2019-10-21 08:51:59 -07:00
seek.c	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
swapfile.c	iomap: Fix negative assignment to unsigned sis->pages in iomap_swapfile_activate	2021-04-07 15:00:04 +02:00
trace.c	iomap: lift common tracing code from xfs to iomap	2019-10-21 08:51:59 -07:00
trace.h	iomap: fall back to buffered writes for invalidation failures	2020-08-05 09:24:16 -07:00