diff options
author | Eric Biggers <ebiggers@google.com> | 2018-01-26 12:15:59 +1100 |
---|---|---|
committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2018-01-29 18:53:59 +1100 |
commit | aec57d30d244438da48d76ad2ec27dfc09c93561 (patch) | |
tree | e7caab04e7efbbb332bbd008a4436704d9407bc2 | |
parent | 6222ad51a117e6e5dcb886ba7c89e82756c8ac4f (diff) | |
download | linux-next-aec57d30d244438da48d76ad2ec27dfc09c93561.tar.gz |
pipe: actually allow root to exceed the pipe buffer limits
pipe-user-pages-hard and pipe-user-pages-soft are only supposed to apply
to unprivileged users, as documented in both Documentation/sysctl/fs.txt
and the pipe(7) man page.
However, the capabilities are actually only checked when increasing a
pipe's size using F_SETPIPE_SZ, not when creating a new pipe. Therefore,
if pipe-user-pages-hard has been set, the root user can run into it and be
unable to create pipes. Similarly, if pipe-user-pages-soft has been set,
the root user can run into it and have their pipes limited to 1 page each.
Fix this by allowing the privileged override in both cases.
Link: http://lkml.kernel.org/r/20180111052902.14409-4-ebiggers3@gmail.com
Fixes: 759c01142a5d ("pipe: limit the per-user amount of pages allocated in pipes")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
-rw-r--r-- | fs/pipe.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index 61adbf0f5b53..04acfad4692b 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -613,6 +613,11 @@ static bool too_many_pipe_buffers_hard(unsigned long user_bufs) return pipe_user_pages_hard && user_bufs >= pipe_user_pages_hard; } +static bool is_unprivileged_user(void) +{ + return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN); +} + struct pipe_inode_info *alloc_pipe_info(void) { struct pipe_inode_info *pipe; @@ -629,12 +634,12 @@ struct pipe_inode_info *alloc_pipe_info(void) user_bufs = account_pipe_buffers(user, 0, pipe_bufs); - if (too_many_pipe_buffers_soft(user_bufs)) { + if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) { user_bufs = account_pipe_buffers(user, pipe_bufs, 1); pipe_bufs = 1; } - if (too_many_pipe_buffers_hard(user_bufs)) + if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user()) goto out_revert_acct; pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer), @@ -1065,7 +1070,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg) if (nr_pages > pipe->buffers && (too_many_pipe_buffers_hard(user_bufs) || too_many_pipe_buffers_soft(user_bufs)) && - !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) { + is_unprivileged_user()) { ret = -EPERM; goto out_revert_acct; } |