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| author | Jens Axboe <jens.axboe@oracle.com> | 2010-05-19 21:03:16 +0200 |
|---|---|---|
| committer | Jens Axboe <jens.axboe@oracle.com> | 2010-05-21 21:12:52 +0200 |
| commit | b492e95be0ae672922f4734acf3f5d35c30be948 (patch) | |
| tree | a8a1e7f035903796e6b8f626add8d269bf989a35 | |
| parent | pipe: add support for shrinking and growing pipes (diff) | |
| download | linux-b492e95be0ae672922f4734acf3f5d35c30be948.tar.xz linux-b492e95be0ae672922f4734acf3f5d35c30be948.zip | |
pipe: set lower and upper limit on max pages in the pipe page array
We need at least two to guarantee proper POSIX behaviour, so
never allow a smaller limit than that.
Also expose a /proc/sys/fs/pipe-max-pages sysctl file that allows
root to define a sane upper limit. Make it default to 16 times the
default size, which is 16 pages.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| -rw-r--r-- | fs/pipe.c | 15 | ||||
| -rw-r--r-- | include/linux/pipe_fs_i.h | 2 | ||||
| -rw-r--r-- | kernel/sysctl.c | 9 |
3 files changed, 26 insertions, 0 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index 054b8a6a2c7a..d79872eba09a 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -19,11 +19,18 @@ #include <linux/pagemap.h> #include <linux/audit.h> #include <linux/syscalls.h> +#include <linux/fcntl.h> #include <asm/uaccess.h> #include <asm/ioctls.h> /* + * The max size that a non-root user is allowed to grow the pipe. Can + * be set by root in /proc/sys/fs/pipe-max-pages + */ +unsigned int pipe_max_pages = PIPE_DEF_BUFFERS * 16; + +/* * We use a start+len construction, which provides full use of the * allocated memory. * -- Florian Coosmann (FGC) @@ -1162,6 +1169,14 @@ long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg) switch (cmd) { case F_SETPIPE_SZ: + if (!capable(CAP_SYS_ADMIN) && arg > pipe_max_pages) + return -EINVAL; + /* + * The pipe needs to be at least 2 pages large to + * guarantee POSIX behaviour. + */ + if (arg < 2) + return -EINVAL; ret = pipe_set_size(pipe, arg); break; case F_GETPIPE_SZ: diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index 65f4282fcbaf..16de3933c45e 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -139,6 +139,8 @@ void pipe_lock(struct pipe_inode_info *); void pipe_unlock(struct pipe_inode_info *); void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *); +extern unsigned int pipe_max_pages; + /* Drop the inode semaphore and wait for a pipe event, atomically */ void pipe_wait(struct pipe_inode_info *pipe); diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 8686b0f5fc12..c649d1c5fe09 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -52,6 +52,7 @@ #include <linux/slow-work.h> #include <linux/perf_event.h> #include <linux/kprobes.h> +#include <linux/pipe_fs_i.h> #include <asm/uaccess.h> #include <asm/processor.h> @@ -1423,6 +1424,14 @@ static struct ctl_table fs_table[] = { .child = binfmt_misc_table, }, #endif + { + .procname = "pipe-max-pages", + .data = &pipe_max_pages, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = &proc_dointvec_minmax, + .extra1 = &two, + }, /* * NOTE: do not add new entries to this table unless you have read * Documentation/sysctl/ctl_unnumbered.txt |