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authorMichael Kerrisk (man-pages) <mtk.manpages@gmail.com>2016-10-11 23:53:43 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-05-26 09:48:51 +0300
commit7d56aed52b52450181c7ba58cb680739cb7e5737 (patch)
tree56028ba8ee1a670fd868e2fd7d849868817ae025 /fs/pipe.c
parente28debec24f5c40ac5752bd2fc3b2e686e9010d0 (diff)
downloadlinux-7d56aed52b52450181c7ba58cb680739cb7e5737.tar.xz
pipe: cap initial pipe capacity according to pipe-max-size limit
commit 086e774a57fba4695f14383c0818994c0b31da7c upstream. 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> Signed-off-by: Daniel Sangorrin <daniel.sangorrin@toshiba.co.jp> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/pipe.c')
-rw-r--r--fs/pipe.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index 39eff9a67253..1e7263bb837a 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -616,6 +616,9 @@ struct pipe_inode_info *alloc_pipe_info(void)
unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
struct user_struct *user = get_current_user();
+ if (pipe_bufs * PAGE_SIZE > pipe_max_size && !capable(CAP_SYS_RESOURCE))
+ pipe_bufs = pipe_max_size >> PAGE_SHIFT;
+
if (!too_many_pipe_buffers_hard(user)) {
if (too_many_pipe_buffers_soft(user))
pipe_bufs = 1;