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authorEric Biggers <ebiggers@google.com>2018-02-06 15:41:53 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-02-06 18:32:47 -0800
commit85c2dd5473b2718b4b63e74bfeb1ca876868e11f (patch)
treeed089d058c979a7ff1b2e70b0087edb7f11bc75b /fs
parent319e0a21bb7823abbb4818fe2724e572bbac77a2 (diff)
downloadlwn-85c2dd5473b2718b4b63e74bfeb1ca876868e11f.tar.gz
lwn-85c2dd5473b2718b4b63e74bfeb1ca876868e11f.zip
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: 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> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/pipe.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index 61adbf0f5b53..04acfad4692b 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -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;
}
+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(void)
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_inode_info *pipe, unsigned long arg)
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;
}