From: Mike Rapoport <rppt@linux.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Daniel Colascione <dancol@google.com>,
Jann Horn <jannh@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Lokesh Gidra <lokeshgidra@google.com>,
Nick Kralevich <nnk@google.com>, Nosh Minwalla <nosh@google.com>,
Pavel Emelyanov <ovzxemul@gmail.com>,
Tim Murray <timmurray@google.com>,
linux-api@vger.kernel.org, linux-mm@kvack.org,
Mike Rapoport <rppt@linux.ibm.com>
Subject: [PATCH 1/1] userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK
Date: Tue, 5 Nov 2019 17:29:37 +0200 [thread overview]
Message-ID: <1572967777-8812-2-git-send-email-rppt@linux.ibm.com> (raw)
In-Reply-To: <1572967777-8812-1-git-send-email-rppt@linux.ibm.com>
Current implementation of UFFD_FEATURE_EVENT_FORK modifies the file
descriptor table from the read() implementation of uffd, which may have
security implications for unprivileged use of the userfaultfd.
Limit availability of UFFD_FEATURE_EVENT_FORK only for callers that have
CAP_SYS_PTRACE.
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
fs/userfaultfd.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index f9fd18670e22..d99d166fd892 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1834,13 +1834,12 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
goto out;
features = uffdio_api.features;
- if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) {
- memset(&uffdio_api, 0, sizeof(uffdio_api));
- if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
- goto out;
- ret = -EINVAL;
- goto out;
- }
+ ret = -EINVAL;
+ if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES))
+ goto err_out;
+ ret = -EPERM;
+ if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE))
+ goto err_out;
/* report all available features and ioctls to userland */
uffdio_api.features = UFFD_API_FEATURES;
uffdio_api.ioctls = UFFD_API_IOCTLS;
@@ -1853,6 +1852,11 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
ret = 0;
out:
return ret;
+err_out:
+ memset(&uffdio_api, 0, sizeof(uffdio_api));
+ if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
+ ret = -EFAULT;
+ goto out;
}
static long userfaultfd_ioctl(struct file *file, unsigned cmd,
--
2.7.4
next prev parent reply other threads:[~2019-11-05 15:29 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-05 15:29 [PATCH 0/1] userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK Mike Rapoport
2019-11-05 15:29 ` Mike Rapoport [this message]
2019-11-05 15:37 ` [PATCH 1/1] " Andrea Arcangeli
2019-11-05 15:55 ` Daniel Colascione
2019-11-05 16:00 ` Andy Lutomirski
2019-11-05 16:06 ` Daniel Colascione
2019-11-05 16:33 ` Andrea Arcangeli
2019-11-05 16:39 ` Daniel Colascione
2019-11-05 16:55 ` Andrea Arcangeli
2019-11-05 17:02 ` Daniel Colascione
2019-11-05 17:30 ` Andrea Arcangeli
2019-11-05 22:01 ` Andy Lutomirski
2019-11-05 22:10 ` Daniel Colascione
2019-11-05 16:24 ` Andrea Arcangeli
2019-11-05 16:41 ` Daniel Colascione
2019-11-07 8:39 ` Mike Rapoport
2019-11-07 8:54 ` Daniel Colascione
2019-11-07 15:38 ` Andrea Arcangeli
2019-11-07 16:15 ` Daniel Colascione
2019-11-07 18:22 ` Andrea Arcangeli
2019-11-07 18:50 ` Daniel Colascione
2019-11-07 19:27 ` Andrea Arcangeli
2019-11-10 17:02 ` Andy Lutomirski
2019-11-05 15:59 ` Aleksa Sarai
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