diff options
| author | Mike Rapoport <rppt@linux.ibm.com> | 2019-11-30 17:58:01 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-01-04 13:59:58 +0100 |
| commit | 36d503a7b0311d989affef48b910d90cbae41057 (patch) | |
| tree | 17b8f84c44a3fff1b52b6eeb96bc28893309f7b2 /fs | |
| parent | 5dc89b665d7278a50997a081ae546115029b2282 (diff) | |
userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK
[ Upstream commit 3c1c24d91ffd536de0a64688a9df7f49e58fadbc ]
A while ago Andy noticed
(http://lkml.kernel.org/r/CALCETrWY+5ynDct7eU_nDUqx=okQvjm=Y5wJvA4ahBja=CQXGw@mail.gmail.com)
that UFFD_FEATURE_EVENT_FORK used by an unprivileged user may have
security implications.
As the first step of the solution the following patch limits the availably
of UFFD_FEATURE_EVENT_FORK only for those having CAP_SYS_PTRACE.
The usage of CAP_SYS_PTRACE ensures compatibility with CRIU.
Yet, if there are other users of non-cooperative userfaultfd that run
without CAP_SYS_PTRACE, they would be broken :(
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.
Link: http://lkml.kernel.org/r/1572967777-8812-2-git-send-email-rppt@linux.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Daniel Colascione <dancol@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Nick Kralevich <nnk@google.com>
Cc: Nosh Minwalla <nosh@google.com>
Cc: Pavel Emelyanov <ovzxemul@gmail.com>
Cc: Tim Murray <timmurray@google.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/userfaultfd.c | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index a609d480606d..e2b2196fd942 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1807,13 +1807,12 @@ 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; @@ -1826,6 +1825,11 @@ 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, |