4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Eric Biggers <ebigg...@google.com> commit 85c2dd5473b2718b4b63e74bfeb1ca876868e11f upstream. 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-ebigge...@gmail.com Fixes: 759c01142a5d ("pipe: limit the per-user amount of pages allocated in pipes") Signed-off-by: Eric Biggers <ebigg...@google.com> Acked-by: Kees Cook <keesc...@chromium.org> Acked-by: Joe Lawrence <joe.lawre...@redhat.com> Cc: Alexander Viro <v...@zeniv.linux.org.uk> Cc: "Luis R . Rodriguez" <mcg...@kernel.org> Cc: Michael Kerrisk <mtk.manpa...@gmail.com> Cc: Mikulas Patocka <mpato...@redhat.com> Cc: Willy Tarreau <w...@1wt.eu> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- fs/pipe.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/fs/pipe.c +++ b/fs/pipe.c @@ -617,6 +617,11 @@ static bool too_many_pipe_buffers_hard(u 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; @@ -633,12 +638,12 @@ struct pipe_inode_info *alloc_pipe_info( 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), @@ -1069,7 +1074,7 @@ static long pipe_set_size(struct pipe_in 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; }
