Commit 85c2dd54 authored by Eric Biggers's avatar Eric Biggers Committed by Linus Torvalds

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@gmail.com
Fixes: 759c0114 ("pipe: limit the per-user amount of pages allocated in pipes")
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarJoe 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>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 319e0a21
...@@ -613,6 +613,11 @@ static bool too_many_pipe_buffers_hard(unsigned long user_bufs) ...@@ -613,6 +613,11 @@ static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
return pipe_user_pages_hard && user_bufs >= pipe_user_pages_hard; 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 *alloc_pipe_info(void)
{ {
struct pipe_inode_info *pipe; struct pipe_inode_info *pipe;
...@@ -629,12 +634,12 @@ struct pipe_inode_info *alloc_pipe_info(void) ...@@ -629,12 +634,12 @@ struct pipe_inode_info *alloc_pipe_info(void)
user_bufs = account_pipe_buffers(user, 0, pipe_bufs); 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); user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
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; goto out_revert_acct;
pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer), pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
...@@ -1065,7 +1070,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg) ...@@ -1065,7 +1070,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
if (nr_pages > pipe->buffers && if (nr_pages > pipe->buffers &&
(too_many_pipe_buffers_hard(user_bufs) || (too_many_pipe_buffers_hard(user_bufs) ||
too_many_pipe_buffers_soft(user_bufs)) && too_many_pipe_buffers_soft(user_bufs)) &&
!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) { is_unprivileged_user()) {
ret = -EPERM; ret = -EPERM;
goto out_revert_acct; goto out_revert_acct;
} }
......
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