Patch "pipe: actually allow root to exceed the pipe buffer limits" has been added to the 4.14-stable tree

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;a=summary

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 <[email protected]> know about it.

From: Eric Biggers <[email protected]>
Date: Tue, 6 Feb 2018 15:41:53 -0800
Subject: pipe: actually allow root to exceed the pipe buffer limits

From: Eric Biggers <[email protected]>

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.

---
 fs/pipe.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

@@ -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 [email protected] 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