mainlining shenanigans
3e338d3c95
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>
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| certs | ||
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| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.