Suren Baghdasaryan 6a7626c479 staging: android: ashmem: Fix lockdep warning for write operation ... commit 3e338d3c95 upstream. syzbot report [1] describes a deadlock when write operation against an ashmem fd executed at the time when ashmem is shrinking its cache results in the following lock sequence: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&sb->s_type->i_mutex_key#13); lock(fs_reclaim); lock(&sb->s_type->i_mutex_key#13); kswapd takes fs_reclaim and then inode_lock while generic_perform_write takes inode_lock and then fs_reclaim. However ashmem does not support writing into backing shmem with a write syscall. The only way to change its content is to mmap it and operate on mapped memory. Therefore the race that lockdep is warning about is not valid. Resolve this by introducing a separate lockdep class for the backing shmem inodes. [1]: https://lkml.kernel.org/lkml/0000000000000b5f9d059aa2037f@google.com/ Reported-by: syzbot+7a0d9d0b26efefe61780@syzkaller.appspotmail.com Signed-off-by: Suren Baghdasaryan <surenb@google.com> Cc: stable <stable@vger.kernel.org> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Link: https://lore.kernel.org/r/20200730192632.3088194-1-surenb@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-08-11 15:33:34 +02:00
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ion	staging: android: ion: use vmap instead of vm_map_ram	2020-06-22 09:30:57 +02:00
uapi	staging: android: ion: Add the GPL exception for syscalls	2019-02-14 10:47:20 +01:00
Kconfig	staging: remove redundant 'default n' from Kconfig	2019-04-16 13:39:01 +02:00
Makefile	staging: add missing SPDX lines to Makefile files	2019-04-03 11:10:15 +02:00
TODO	staging: android: Remove ion device tree bindings from the TODO	2019-08-21 05:48:06 -07:00
ashmem.c	staging: android: ashmem: Fix lockdep warning for write operation	2020-08-11 15:33:34 +02:00
ashmem.h	staging: android: Clean up license identifiers	2018-05-08 13:24:15 +02:00
vsoc.c	hrtimer/treewide: Use hrtimer_sleeper_start_expires()	2019-08-01 17:43:16 +02:00