The patch titled
Subject: pipe: actually allow root to exceed the pipe buffer limits
has been added to the -mm tree. Its filename is
pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits.patch
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------------------------------------------------------
From: Eric Biggers <ebiggers@xxxxxxxxxx>
Subject: 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@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>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/pipe.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff -puN fs/pipe.c~pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits fs/pipe.c
--- a/fs/pipe.c~pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits
+++ a/fs/pipe.c
@@ -613,6 +613,11 @@ 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;
@@ -629,12 +634,12 @@ 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),
@@ -1065,7 +1070,7 @@ 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 -mm which might be from ebiggers@xxxxxxxxxx are
userfaultfd-convert-to-use-anon_inode_getfd.patch
pipe-sysctl-drop-min-parameter-from-pipe-max-size-converter.patch
pipe-sysctl-remove-pipe_proc_fn.patch
pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits.patch
pipe-fix-off-by-one-error-when-checking-buffer-limits.patch
pipe-reject-f_setpipe_sz-with-size-over-uint_max.patch
pipe-simplify-round_pipe_size.patch
pipe-read-buffer-limits-atomically.patch