c575076ba4
[ Upstream commit 355f074609dbf3042900ea9d30fcd2b0c323a365 ] syzbot reported: | BUG: KCSAN: data-race in p9_fd_create / p9_fd_create | | read-write to 0xffff888130fb3d48 of 4 bytes by task 15599 on cpu 0: | p9_fd_open net/9p/trans_fd.c:842 [inline] | p9_fd_create+0x210/0x250 net/9p/trans_fd.c:1092 | p9_client_create+0x595/0xa70 net/9p/client.c:1010 | v9fs_session_init+0xf9/0xd90 fs/9p/v9fs.c:410 | v9fs_mount+0x69/0x630 fs/9p/vfs_super.c:123 | legacy_get_tree+0x74/0xd0 fs/fs_context.c:611 | vfs_get_tree+0x51/0x190 fs/super.c:1519 | do_new_mount+0x203/0x660 fs/namespace.c:3335 | path_mount+0x496/0xb30 fs/namespace.c:3662 | do_mount fs/namespace.c:3675 [inline] | __do_sys_mount fs/namespace.c:3884 [inline] | [...] | | read-write to 0xffff888130fb3d48 of 4 bytes by task 15563 on cpu 1: | p9_fd_open net/9p/trans_fd.c:842 [inline] | p9_fd_create+0x210/0x250 net/9p/trans_fd.c:1092 | p9_client_create+0x595/0xa70 net/9p/client.c:1010 | v9fs_session_init+0xf9/0xd90 fs/9p/v9fs.c:410 | v9fs_mount+0x69/0x630 fs/9p/vfs_super.c:123 | legacy_get_tree+0x74/0xd0 fs/fs_context.c:611 | vfs_get_tree+0x51/0x190 fs/super.c:1519 | do_new_mount+0x203/0x660 fs/namespace.c:3335 | path_mount+0x496/0xb30 fs/namespace.c:3662 | do_mount fs/namespace.c:3675 [inline] | __do_sys_mount fs/namespace.c:3884 [inline] | [...] | | value changed: 0x00008002 -> 0x00008802 Within p9_fd_open(), O_NONBLOCK is added to f_flags of the read and write files. This may happen concurrently if e.g. mounting process modifies the fd in another thread. Mark the plain read-modify-writes as intentional data-races, with the assumption that the result of executing the accesses concurrently will always result in the same result despite the accesses themselves not being atomic. Reported-by: syzbot+e441aeeb422763cc5511@syzkaller.appspotmail.com Signed-off-by: Marco Elver <elver@google.com> Link: https://lore.kernel.org/r/ZO38mqkS0TYUlpFp@elver.google.com Signed-off-by: Dominique Martinet <asmadeus@codewreck.org> Message-ID: <20231025103445.1248103-1-asmadeus@codewreck.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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.