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authorLinus Torvalds <torvalds@linux-foundation.org>2022-10-03 17:51:52 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-10-03 17:51:52 -0700
commit26b84401da8458c5cbd6818d5732f7bbb84124a2 (patch)
treef73ae58b98f9c4ea5734597d06926c9da44cc41a /fs/userfaultfd.c
parente816da29bc0cf0504afddd314a2d71b694b5d7af (diff)
parent1e7d8bcbe37d3c63babe628443f13f77970dd06b (diff)
Merge tag 'lsm-pr-20221003' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm
Pull LSM updates from Paul Moore: "Seven patches for the LSM layer and we've got a mix of trivial and significant patches. Highlights below, starting with the smaller bits first so they don't get lost in the discussion of the larger items: - Remove some redundant NULL pointer checks in the common LSM audit code. - Ratelimit the lockdown LSM's access denial messages. With this change there is a chance that the last visible lockdown message on the console is outdated/old, but it does help preserve the initial series of lockdown denials that started the denial message flood and my gut feeling is that these might be the more valuable messages. - Open userfaultfds as readonly instead of read/write. While this code obviously lives outside the LSM, it does have a noticeable impact on the LSMs with Ondrej explaining the situation in the commit description. It is worth noting that this patch languished on the VFS list for over a year without any comments (objections or otherwise) so I took the liberty of pulling it into the LSM tree after giving fair notice. It has been in linux-next since the end of August without any noticeable problems. - Add a LSM hook for user namespace creation, with implementations for both the BPF LSM and SELinux. Even though the changes are fairly small, this is the bulk of the diffstat as we are also including BPF LSM selftests for the new hook. It's also the most contentious of the changes in this pull request with Eric Biederman NACK'ing the LSM hook multiple times during its development and discussion upstream. While I've never taken NACK's lightly, I'm sending these patches to you because it is my belief that they are of good quality, satisfy a long-standing need of users and distros, and are in keeping with the existing nature of the LSM layer and the Linux Kernel as a whole. The patches in implement a LSM hook for user namespace creation that allows for a granular approach, configurable at runtime, which enables both monitoring and control of user namespaces. The general consensus has been that this is far preferable to the other solutions that have been adopted downstream including outright removal from the kernel, disabling via system wide sysctls, or various other out-of-tree mechanisms that users have been forced to adopt since we haven't been able to provide them an upstream solution for their requests. Eric has been steadfast in his objections to this LSM hook, explaining that any restrictions on the user namespace could have significant impact on userspace. While there is the possibility of impacting userspace, it is important to note that this solution only impacts userspace when it is requested based on the runtime configuration supplied by the distro/admin/user. Frederick (the pathset author), the LSM/security community, and myself have tried to work with Eric during development of this patchset to find a mutually acceptable solution, but Eric's approach and unwillingness to engage in a meaningful way have made this impossible. I have CC'd Eric directly on this pull request so he has a chance to provide his side of the story; there have been no objections outside of Eric's" * tag 'lsm-pr-20221003' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm: lockdown: ratelimit denial messages userfaultfd: open userfaultfds with O_RDONLY selinux: Implement userns_create hook selftests/bpf: Add tests verifying bpf lsm userns_create hook bpf-lsm: Make bpf_lsm_userns_create() sleepable security, lsm: Introduce security_create_user_ns() lsm: clean up redundant NULL pointer check
Diffstat (limited to 'fs/userfaultfd.c')
-rw-r--r--fs/userfaultfd.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 175de70e3adf..0c1d33c4f74c 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -991,7 +991,7 @@ static int resolve_userfault_fork(struct userfaultfd_ctx *new,
int fd;
fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, new,
- O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode);
+ O_RDONLY | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode);
if (fd < 0)
return fd;
@@ -2094,7 +2094,7 @@ SYSCALL_DEFINE1(userfaultfd, int, flags)
mmgrab(ctx->mm);
fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, ctx,
- O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL);
+ O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL);
if (fd < 0) {
mmdrop(ctx->mm);
kmem_cache_free(userfaultfd_ctx_cachep, ctx);