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 4.9-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-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 85c2dd5473b2718b4b63e74bfeb1ca876868e11f Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@xxxxxxxxxx>
Date: Tue, 6 Feb 2018 15:41:53 -0800
Subject: pipe: actually allow root to exceed the pipe buffer limits
From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxx
Fixes: 759c01142a5d ("pipe: limit the per-user amount of pages allocated in pipes")
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: "Luis R . Rodriguez" <mcgrof@xxxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: Willy Tarreau <w@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;
}
Patches currently in stable-queue which might be from ebiggers@xxxxxxxxxx are
queue-4.9/pipe-fix-off-by-one-error-when-checking-buffer-limits.patch
queue-4.9/crypto-cryptd-pass-through-absence-of-setkey.patch
queue-4.9/pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits.patch
queue-4.9/kernel-relay.c-revert-kernel-relay.c-fix-potential-memory-leak.patch
queue-4.9/nfs-reject-request-for-id_legacy-key-without-auxdata.patch
queue-4.9/crypto-poly1305-remove-setkey-method.patch
queue-4.9/crypto-sha512-mb-initialize-pending-lengths-correctly.patch
queue-4.9/crypto-hash-introduce-crypto_hash_alg_has_setkey.patch
queue-4.9/crypto-mcryptd-pass-through-absence-of-setkey.patch