This is a note to let you know that I've just added the patch titled
pipe: actually allow root to exceed the pipe buffer limits
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 85c2dd5473b2718b4b63e74bfeb1ca876868e11f Mon Sep 17 00:00:00 2001
From: Eric Biggers ebiggers@google.com Date: Tue, 6 Feb 2018 15:41:53 -0800 Subject: pipe: actually allow root to exceed the pipe buffer limits
From: Eric Biggers ebiggers@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-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 Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/pipe.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
--- a/fs/pipe.c +++ b/fs/pipe.c @@ -618,6 +618,11 @@ 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; @@ -634,12 +639,12 @@ 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; }
Patches currently in stable-queue which might be from ebiggers@google.com are
queue-4.14/pipe-fix-off-by-one-error-when-checking-buffer-limits.patch queue-4.14/crypto-hash-annotate-algorithms-taking-optional-key.patch queue-4.14/crypto-cryptd-pass-through-absence-of-setkey.patch queue-4.14/crypto-hash-prevent-using-keyed-hashes-without-setting-key.patch queue-4.14/ubifs-free-the-encrypted-symlink-target.patch queue-4.14/pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits.patch queue-4.14/kernel-relay.c-revert-kernel-relay.c-fix-potential-memory-leak.patch queue-4.14/nfs-reject-request-for-id_legacy-key-without-auxdata.patch queue-4.14/crypto-poly1305-remove-setkey-method.patch queue-4.14/crypto-sha512-mb-initialize-pending-lengths-correctly.patch queue-4.14/crypto-hash-introduce-crypto_hash_alg_has_setkey.patch queue-4.14/crypto-mcryptd-pass-through-absence-of-setkey.patch