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android_kernel_google_msm/fs/fuse
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Roman Gushchin 2b1264df0c fuse: break infinite loop in fuse_fill_write_pages() 
I got a report about unkillable task eating CPU. Further
investigation shows, that the problem is in the fuse_fill_write_pages()
function. If iov's first segment has zero length, we get an infinite
loop, because we never reach iov_iter_advance() call.

Fix this by calling iov_iter_advance() before repeating an attempt to
copy data from userspace.

A similar problem is described in 124d3b7041 ("fix writev regression:
pan hanging unkillable and un-straceable"). If zero-length segmend
is followed by segment with invalid address,
iov_iter_fault_in_readable() checks only first segment (zero-length),
iov_iter_copy_from_user_atomic() skips it, fails at second and
returns zero -> goto again without skipping zero-length segment.

Patch calls iov_iter_advance() before goto again: we'll skip zero-length
segment at second iteraction and iov_iter_fault_in_readable() will detect
invalid address.

Special thanks to Konstantin Khlebnikov, who helped a lot with the commit
description.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Maxim Patlasov <mpatlasov@parallels.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Roman Gushchin <klamm@yandex-team.ru>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Fixes: ea9b9907b8 ("fuse: implement perform_write")
Cc: <stable@vger.kernel.org>

Change-Id: Id37193373294dd43191469389cfe68ca1736a54b
2016-10-29 23:12:16 +08:00
..
control.c filesystems: add set_nlink() 2011-11-02 12:53:43 +01:00
cuse.c fs: add module.h to files that were implicitly using it 2011-10-31 19:30:31 -04:00
dev.c fuse: Freeze client on suspend when request sent to userspace 2013-02-20 02:49:29 -08:00
dir.c fuse: O_DIRECT support for files 2012-03-05 15:48:11 +01:00
file.c fuse: break infinite loop in fuse_fill_write_pages() 2016-10-29 23:12:16 +08:00
fuse_i.h Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse 2012-01-12 12:39:21 -08:00
inode.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse 2012-04-18 17:29:05 -07:00
Kconfig fs/Kconfig: move fuse out 2009-01-22 13:15:55 +03:00
Makefile CUSE: implement CUSE - Character device in Userspace 2009-06-09 11:24:11 +02:00