author: Lokesh Gidra <lokeshgidra@google.com> 2020-12-14 19:13:49 -0800
committer: Linus Torvalds <torvalds@linux-foundation.org> 2020-12-15 12:13:46 -0800
commit: 37cd0575b8510159992d279c530c05f872990b02
parent: f289041ed4cf9a3f6e8a32068fef9ffb2acc5662
Commit Summary:
Diffstat:
1 file changed, 9 insertions, 1 deletion
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 000b457ad087..605599fde015 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -405,6 +405,13 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
if (ctx->features & UFFD_FEATURE_SIGBUS)
goto out;
+ if ((vmf->flags & FAULT_FLAG_USER) == 0 &&
+ ctx->flags & UFFD_USER_MODE_ONLY) {
+ printk_once(KERN_WARNING "uffd: Set unprivileged_userfaultfd "
+ "sysctl knob to 1 if kernel faults must be handled "
+ "without obtaining CAP_SYS_PTRACE capability\n");
+ goto out;
+ }
/*
* If it's already released don't get it. This avoids to loop
@@ -1965,10 +1972,11 @@ SYSCALL_DEFINE1(userfaultfd, int, flags)
BUG_ON(!current->mm);
/* Check the UFFD_* constants for consistency. */
+ BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UFFD_SHARED_FCNTL_FLAGS);
BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC);
BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK);
- if (flags & ~UFFD_SHARED_FCNTL_FLAGS)
+ if (flags & ~(UFFD_SHARED_FCNTL_FLAGS | UFFD_USER_MODE_ONLY))
return -EINVAL;
ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);