[PATCH 6.6 046/396] fuse: fix VM_MAYSHARE and direct_io_allow_mmap

Greg Kroah-Hartman
2024-04-01T16:37:12Z

From: Bernd Schubert <bschubert@ddn.com>

[ Upstream commit 9511176bbaee0ac60ecc84e7b01cf5972a59ea17 ]

There were multiple issues with direct_io_allow_mmap:

- fuse_link_write_file() was missing, resulting in warnings in
fuse_write_file_get() and EIO from msync()

- "vma->vm_ops = &fuse_file_vm_ops" was not set, but especially
fuse_page_mkwrite is needed.

The semantics of invalidate_inode_pages2() is so far not clearly defined in
fuse_file_mmap. It dates back to commit 3121bfe76311 ("fuse: fix
"direct_io" private mmap") Though, as direct_io_allow_mmap is a new
feature, that was for MAP_PRIVATE only. As invalidate_inode_pages2() is
calling into fuse_launder_folio() and writes out dirty pages, it should be
safe to call invalidate_inode_pages2 for MAP_PRIVATE and MAP_SHARED as
well.

Cc: Hao Xu <howeyxu@tencent.com>
Cc: stable@vger.kernel.org
Fixes: e78662e818f9 ("fuse: add a new fuse init flag to relax restrictions in no cache mode")
Signed-off-by: Bernd Schubert <bschubert@ddn.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/fuse/file.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index a660f1f21540a..cc9651a01351c 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2467,7 +2467,8 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
return fuse_dax_mmap(file, vma);

if (ff->open_flags & FOPEN_DIRECT_IO) {
- /* Can't provide the coherency needed for MAP_SHARED
+ /*
+ * Can't provide the coherency needed for MAP_SHARED
* if FUSE_DIRECT_IO_ALLOW_MMAP isn't set.
*/
if ((vma->vm_flags & VM_MAYSHARE) && !fc->direct_io_allow_mmap)
@@ -2475,7 +2476,10 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)

invalidate_inode_pages2(file->f_mapping);

- return generic_file_mmap(file, vma);
+ if (!(vma->vm_flags & VM_MAYSHARE)) {
+ /* MAP_PRIVATE */
+ return generic_file_mmap(file, vma);
+ }
}

if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
--
2.43.0