Patch "fuse: Apply flags2 only when userspace set the FUSE_INIT_EXT" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    fuse: Apply flags2 only when userspace set the FUSE_INIT_EXT

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fuse-apply-flags2-only-when-userspace-set-the-fuse_init_ext.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 3066ff93476c35679cb07a97cce37d9bb07632ff Mon Sep 17 00:00:00 2001
From: Bernd Schubert <bschubert@xxxxxxx>
Date: Fri, 15 Apr 2022 13:53:56 +0200
Subject: fuse: Apply flags2 only when userspace set the FUSE_INIT_EXT

From: Bernd Schubert <bschubert@xxxxxxx>

commit 3066ff93476c35679cb07a97cce37d9bb07632ff upstream.

This is just a safety precaution to avoid checking flags on memory that was
initialized on the user space side.  libfuse zeroes struct fuse_init_out
outarg, but this is not guranteed to be done in all implementations.
Better is to act on flags and to only apply flags2 when FUSE_INIT_EXT is
set.

There is a risk with this change, though - it might break existing user
space libraries, which are already using flags2 without setting
FUSE_INIT_EXT.

The corresponding libfuse patch is here
https://github.com/libfuse/libfuse/pull/662

Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
Fixes: 53db28933e95 ("fuse: extend init flags")
Cc: <stable@xxxxxxxxxxxxxxx> # v5.17
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/fuse/inode.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1127,7 +1127,10 @@ static void process_init_reply(struct fu
 		process_init_limits(fc, arg);
 
 		if (arg->minor >= 6) {
-			u64 flags = arg->flags | (u64) arg->flags2 << 32;
+			u64 flags = arg->flags;
+
+			if (flags & FUSE_INIT_EXT)
+				flags |= (u64) arg->flags2 << 32;
 
 			ra_pages = arg->max_readahead / PAGE_SIZE;
 			if (flags & FUSE_ASYNC_READ)


Patches currently in stable-queue which might be from bschubert@xxxxxxx are

queue-6.1/fuse-apply-flags2-only-when-userspace-set-the-fuse_init_ext.patch



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