convert the majority of file systems to mmap_prepare

[PATCH 03/10] fs: consistently use file_has_valid_mmap_hooks() helper

Posted by Lorenzo Stoakes 3 months, 3 weeks ago

Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
callback"), the f_op->mmap() hook has been deprecated in favour of
f_op->mmap_prepare().

Additionally, commit bb666b7c2707 ("mm: add mmap_prepare() compatibility
layer for nested file systems") permits the use of the .mmap_prepare() hook
even in nested filesystems like overlayfs.

There are a number of places where we check only for f_op->mmap - this is
incorrect now mmap_prepare exists, so update all of these to use the
general helper file_has_valid_mmap_hooks().

Most notably, this updates the elf logic to allow for the ability to
execute binaries on filesystems which have the .mmap_prepare hook, but
additionally we update nested filesystems.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
 fs/backing-file.c     | 2 +-
 fs/binfmt_elf.c       | 4 ++--
 fs/binfmt_elf_fdpic.c | 2 +-
 fs/coda/file.c        | 2 +-
 fs/ecryptfs/file.c    | 2 +-
 5 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/backing-file.c b/fs/backing-file.c
index 04018679bf69..5761db9a52a9 100644
--- a/fs/backing-file.c
+++ b/fs/backing-file.c
@@ -333,7 +333,7 @@ int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
 	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))
 		return -EIO;
 
-	if (!file->f_op->mmap)
+	if (!file_has_valid_mmap_hooks(file))
 		return -ENODEV;
 
 	vma_set_file(vma, file);
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index a43363d593e5..a6750bd9392a 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -646,7 +646,7 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
 	if (!elf_check_arch(interp_elf_ex) ||
 	    elf_check_fdpic(interp_elf_ex))
 		goto out;
-	if (!interpreter->f_op->mmap)
+	if (!file_has_valid_mmap_hooks(interpreter))
 		goto out;
 
 	total_size = total_mapping_size(interp_elf_phdata,
@@ -848,7 +848,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		goto out;
 	if (elf_check_fdpic(elf_ex))
 		goto out;
-	if (!bprm->file->f_op->mmap)
+	if (!file_has_valid_mmap_hooks(bprm->file))
 		goto out;
 
 	elf_phdata = load_elf_phdrs(elf_ex, bprm->file);
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 9133f3827f90..699bb9a65c27 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -109,7 +109,7 @@ static int is_elf(struct elfhdr *hdr, struct file *file)
 		return 0;
 	if (!elf_check_arch(hdr))
 		return 0;
-	if (!file->f_op->mmap)
+	if (!file_has_valid_mmap_hooks(file))
 		return 0;
 	return 1;
 }
diff --git a/fs/coda/file.c b/fs/coda/file.c
index 2e6ea9319b35..eed45a80e9bc 100644
--- a/fs/coda/file.c
+++ b/fs/coda/file.c
@@ -160,7 +160,7 @@ coda_file_mmap(struct file *coda_file, struct vm_area_struct *vma)
 	size_t count;
 	int ret;
 
-	if (!host_file->f_op->mmap)
+	if (!file_has_valid_mmap_hooks(host_file))
 		return -ENODEV;
 
 	if (WARN_ON(coda_file != vma->vm_file))
diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index ce0a3c5ed0ca..2bd50d1de5ef 100644
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -193,7 +193,7 @@ static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
 	 * natively.  If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
 	 * allows recursive mounting, this will need to be extended.
 	 */
-	if (!lower_file->f_op->mmap)
+	if (!file_has_valid_mmap_hooks(lower_file))
 		return -ENODEV;
 	return generic_file_mmap(file, vma);
 }
-- 
2.49.0

Re: [PATCH 03/10] fs: consistently use file_has_valid_mmap_hooks() helper

Posted by Christoph Hellwig 3 months, 3 weeks ago

On Mon, Jun 16, 2025 at 08:33:22PM +0100, Lorenzo Stoakes wrote:
> Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
> callback"), the f_op->mmap() hook has been deprecated in favour of
> f_op->mmap_prepare().
> 
> Additionally, commit bb666b7c2707 ("mm: add mmap_prepare() compatibility
> layer for nested file systems") permits the use of the .mmap_prepare() hook
> even in nested filesystems like overlayfs.
> 
> There are a number of places where we check only for f_op->mmap - this is
> incorrect now mmap_prepare exists, so update all of these to use the
> general helper file_has_valid_mmap_hooks().
> 
> Most notably, this updates the elf logic to allow for the ability to
> execute binaries on filesystems which have the .mmap_prepare hook, but
> additionally we update nested filesystems.

Can you please give the function a better name before spreading it?
file operations aren't hooks by any classic definition.

Re: [PATCH 03/10] fs: consistently use file_has_valid_mmap_hooks() helper

Posted by Lorenzo Stoakes 3 months, 3 weeks ago

On Mon, Jun 16, 2025 at 10:11:28PM -0700, Christoph Hellwig wrote:
> On Mon, Jun 16, 2025 at 08:33:22PM +0100, Lorenzo Stoakes wrote:
> > Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
> > callback"), the f_op->mmap() hook has been deprecated in favour of
> > f_op->mmap_prepare().
> >
> > Additionally, commit bb666b7c2707 ("mm: add mmap_prepare() compatibility
> > layer for nested file systems") permits the use of the .mmap_prepare() hook
> > even in nested filesystems like overlayfs.
> >
> > There are a number of places where we check only for f_op->mmap - this is
> > incorrect now mmap_prepare exists, so update all of these to use the
> > general helper file_has_valid_mmap_hooks().
> >
> > Most notably, this updates the elf logic to allow for the ability to
> > execute binaries on filesystems which have the .mmap_prepare hook, but
> > additionally we update nested filesystems.
>
> Can you please give the function a better name before spreading it?
> file operations aren't hooks by any classic definition.
>

can_mmap_file()?

Re: [PATCH 03/10] fs: consistently use file_has_valid_mmap_hooks() helper

Posted by Jan Kara 3 months, 3 weeks ago

On Tue 17-06-25 06:25:34, Lorenzo Stoakes wrote:
> On Mon, Jun 16, 2025 at 10:11:28PM -0700, Christoph Hellwig wrote:
> > On Mon, Jun 16, 2025 at 08:33:22PM +0100, Lorenzo Stoakes wrote:
> > > Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
> > > callback"), the f_op->mmap() hook has been deprecated in favour of
> > > f_op->mmap_prepare().
> > >
> > > Additionally, commit bb666b7c2707 ("mm: add mmap_prepare() compatibility
> > > layer for nested file systems") permits the use of the .mmap_prepare() hook
> > > even in nested filesystems like overlayfs.
> > >
> > > There are a number of places where we check only for f_op->mmap - this is
> > > incorrect now mmap_prepare exists, so update all of these to use the
> > > general helper file_has_valid_mmap_hooks().
> > >
> > > Most notably, this updates the elf logic to allow for the ability to
> > > execute binaries on filesystems which have the .mmap_prepare hook, but
> > > additionally we update nested filesystems.
> >
> > Can you please give the function a better name before spreading it?
> > file operations aren't hooks by any classic definition.
> >
> 
> can_mmap_file()?

I like this name more as well :). With this patch looks good to me. Again a
note that Fixes tag would be probably appropriate for this patch...

								Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH 03/10] fs: consistently use file_has_valid_mmap_hooks() helper

Posted by Christian Brauner 3 months, 3 weeks ago

On Tue, Jun 17, 2025 at 12:08:13PM +0200, Jan Kara wrote:
> On Tue 17-06-25 06:25:34, Lorenzo Stoakes wrote:
> > On Mon, Jun 16, 2025 at 10:11:28PM -0700, Christoph Hellwig wrote:
> > > On Mon, Jun 16, 2025 at 08:33:22PM +0100, Lorenzo Stoakes wrote:
> > > > Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
> > > > callback"), the f_op->mmap() hook has been deprecated in favour of
> > > > f_op->mmap_prepare().
> > > >
> > > > Additionally, commit bb666b7c2707 ("mm: add mmap_prepare() compatibility
> > > > layer for nested file systems") permits the use of the .mmap_prepare() hook
> > > > even in nested filesystems like overlayfs.
> > > >
> > > > There are a number of places where we check only for f_op->mmap - this is
> > > > incorrect now mmap_prepare exists, so update all of these to use the
> > > > general helper file_has_valid_mmap_hooks().
> > > >
> > > > Most notably, this updates the elf logic to allow for the ability to
> > > > execute binaries on filesystems which have the .mmap_prepare hook, but
> > > > additionally we update nested filesystems.
> > >
> > > Can you please give the function a better name before spreading it?
> > > file operations aren't hooks by any classic definition.
> > >
> > 
> > can_mmap_file()?
> 
> I like this name more as well :). With this patch looks good to me. Again a

Fixed in-tree.

Re: [PATCH 03/10] fs: consistently use file_has_valid_mmap_hooks() helper

Posted by Christoph Hellwig 3 months, 3 weeks ago

On Tue, Jun 17, 2025 at 06:25:34AM +0100, Lorenzo Stoakes wrote:
> > > Most notably, this updates the elf logic to allow for the ability to
> > > execute binaries on filesystems which have the .mmap_prepare hook, but
> > > additionally we update nested filesystems.
> >
> > Can you please give the function a better name before spreading it?
> > file operations aren't hooks by any classic definition.
> >
> 
> can_mmap_file()?

Sounds reasonable.

Re: [PATCH 03/10] fs: consistently use file_has_valid_mmap_hooks() helper

Posted by Kees Cook 3 months, 3 weeks ago


On June 16, 2025 12:33:22 PM PDT, Lorenzo Stoakes <lorenzo.stoakes@oracle.com> wrote:
>Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
>callback"), the f_op->mmap() hook has been deprecated in favour of
>f_op->mmap_prepare().
>
>Additionally, commit bb666b7c2707 ("mm: add mmap_prepare() compatibility
>layer for nested file systems") permits the use of the .mmap_prepare() hook
>even in nested filesystems like overlayfs.
>
>There are a number of places where we check only for f_op->mmap - this is
>incorrect now mmap_prepare exists, so update all of these to use the
>general helper file_has_valid_mmap_hooks().
>
>Most notably, this updates the elf logic to allow for the ability to
>execute binaries on filesystems which have the .mmap_prepare hook, but
>additionally we update nested filesystems.
>
>Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
>---
> fs/backing-file.c     | 2 +-
> fs/binfmt_elf.c       | 4 ++--
> fs/binfmt_elf_fdpic.c | 2 +-

Thanks for the refactoring!

Acked-by: Kees Cook<kees@kernel.org>


-- 
Kees Cook