[PATCH] x86/compat: Pull huge_encode_dev() outside of UACCESS

[Peter Zijlstra]

On Mon, Jan 04, 2021 at 09:31:27AM -0600, Josh Poimboeuf wrote:
> Peter, care to submit a proper patch?

Here goes..

---
Subject: x86/compat: Pull huge_encode_dev() outside of UACCESS
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Mon, 4 Jan 2021 13:28:25 +0100

Fixes the following warning:

  arch/x86/kernel/sys_ia32.o: warning: objtool: cp_stat64()+0xd8: call to new_encode_dev() with UACCESS enabled

Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 arch/x86/kernel/sys_ia32.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/sys_ia32.c
+++ b/arch/x86/kernel/sys_ia32.c
@@ -133,18 +133,23 @@ static int cp_stat64(struct stat64 __use
 {
 	typeof(ubuf->st_uid) uid = 0;
 	typeof(ubuf->st_gid) gid = 0;
+	u64 dev, rdev;
+
 	SET_UID(uid, from_kuid_munged(current_user_ns(), stat->uid));
 	SET_GID(gid, from_kgid_munged(current_user_ns(), stat->gid));
+	dev = huge_encode_dev(stat->dev);
+	rdev = huge_encode_dev(stat->rdev);
+
 	if (!user_write_access_begin(ubuf, sizeof(struct stat64)))
 		return -EFAULT;
-	unsafe_put_user(huge_encode_dev(stat->dev), &ubuf->st_dev, Efault);
+	unsafe_put_user(dev, &ubuf->st_dev, Efault);
 	unsafe_put_user(stat->ino, &ubuf->__st_ino, Efault);
 	unsafe_put_user(stat->ino, &ubuf->st_ino, Efault);
 	unsafe_put_user(stat->mode, &ubuf->st_mode, Efault);
 	unsafe_put_user(stat->nlink, &ubuf->st_nlink, Efault);
 	unsafe_put_user(uid, &ubuf->st_uid, Efault);
 	unsafe_put_user(gid, &ubuf->st_gid, Efault);
-	unsafe_put_user(huge_encode_dev(stat->rdev), &ubuf->st_rdev, Efault);
+	unsafe_put_user(rdev, &ubuf->st_rdev, Efault);
 	unsafe_put_user(stat->size, &ubuf->st_size, Efault);
 	unsafe_put_user(stat->atime.tv_sec, &ubuf->st_atime, Efault);
 	unsafe_put_user(stat->atime.tv_nsec, &ubuf->st_atime_nsec, Efault);