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| author | Michael Kerrisk (man-pages) <mtk.manpages@gmail.com> | 2016-10-11 13:53:43 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-11 15:06:32 -0700 |
| commit | 086e774a57fba4695f14383c0818994c0b31da7c (patch) | |
| tree | c8c9ced5e9fca1f95ba2caedd08278da10fa3aae | |
| parent | 9c87bcf0a31b338dc8a69a5d251a037565a94e13 (diff) | |
| download | linux-086e774a57fba4695f14383c0818994c0b31da7c.tar.bz2 | |
pipe: cap initial pipe capacity according to pipe-max-size limit
This is a patch that provides behavior that is more consistent, and
probably less surprising to users. I consider the change optional, and
welcome opinions about whether it should be applied.
By default, pipes are created with a capacity of 64 kiB. However,
/proc/sys/fs/pipe-max-size may be set smaller than this value. In this
scenario, an unprivileged user could thus create a pipe whose initial
capacity exceeds the limit. Therefore, it seems logical to cap the
initial pipe capacity according to the value of pipe-max-size.
The test program shown earlier in this patch series can be used to
demonstrate the effect of the change brought about with this patch:
# cat /proc/sys/fs/pipe-max-size
1048576
# sudo -u mtk ./test_F_SETPIPE_SZ 1
Initial pipe capacity: 65536
# echo 10000 > /proc/sys/fs/pipe-max-size
# cat /proc/sys/fs/pipe-max-size
16384
# sudo -u mtk ./test_F_SETPIPE_SZ 1
Initial pipe capacity: 16384
# ./test_F_SETPIPE_SZ 1
Initial pipe capacity: 65536
The last two executions of 'test_F_SETPIPE_SZ' show that pipe-max-size
caps the initial allocation for a new pipe for unprivileged users, but
not for privileged users.
Link: http://lkml.kernel.org/r/31dc7064-2a17-9c5b-1df1-4e3012ee992c@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/pipe.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index 5ff02c4afe9f..8e0d9f26dfad 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -628,6 +628,9 @@ struct pipe_inode_info *alloc_pipe_info(void) if (pipe == NULL) goto out_free_uid; + if (pipe_bufs * PAGE_SIZE > pipe_max_size && !capable(CAP_SYS_RESOURCE)) + pipe_bufs = pipe_max_size >> PAGE_SHIFT; + user_bufs = account_pipe_buffers(user, 0, pipe_bufs); if (too_many_pipe_buffers_soft(user_bufs)) { |