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authorLinus Torvalds <torvalds@linux-foundation.org>2019-09-12 14:50:14 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2019-09-12 14:50:14 +0100
commit98dcb386e5c3d53da2ed0b14b5930a01c90ad36a (patch)
parent95217783b7f6f331e7a6675e0a31fb9a5a1b9a36 (diff)
parenta0eb9abd8af92d1aa34bc1e24dfbd1ba0bd6a56c (diff)
Merge tag 'for-linus-20190912' of gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux
Pull clone3 fix from Christian Brauner: "This is a last-minute bugfix for clone3() that should go in before we release 5.3 with clone3(). clone3() did not verify that the exit_signal argument was set to a valid signal. This can be used to cause a crash by specifying a signal greater than NSIG. e.g. -1. The commit from Eugene adds a check to copy_clone_args_from_user() to verify that the exit signal is limited by CSIGNAL as with legacy clone() and that the signal is valid. With this we don't get the legacy clone behavior were an invalid signal could be handed down and would only be detected and then ignored in do_notify_parent(). Users of clone3() will now get a proper error right when they pass an invalid exit signal. Note, that this is not a change in user-visible behavior since no kernel with clone3() has been released yet" * tag 'for-linus-20190912' of gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux: fork: block invalid exit signals with clone3()
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 2852d0e76ea3..541fd805fb88 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2338,6 +2338,8 @@ struct mm_struct *copy_init_mm(void)
* It copies the process, and if successful kick-starts
* it and waits for it to finish using the VM if required.
+ *
+ * args->exit_signal is expected to be checked for sanity by the caller.
long _do_fork(struct kernel_clone_args *args)
@@ -2562,6 +2564,14 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
if (copy_from_user(&args, uargs, size))
return -EFAULT;
+ /*
+ * Verify that higher 32bits of exit_signal are unset and that
+ * it is a valid signal
+ */
+ if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
+ !valid_signal(args.exit_signal)))
+ return -EINVAL;
*kargs = (struct kernel_clone_args){
.flags = args.flags,
.pidfd = u64_to_user_ptr(args.pidfd),