The patch titled
Subject: mm/memfd: refactor and cleanup the logic in memfd_create()
has been added to the -mm mm-unstable branch. Its filename is
mm-memfd-refactor-and-cleanup-the-logic-in-memfd_create.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memfd-refactor-and-cleanup-the-logic-in-memfd_create.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Isaac J. Manjarres" <isaacmanjarres@xxxxxxxxxx>
Subject: mm/memfd: refactor and cleanup the logic in memfd_create()
Date: Thu, 9 Jan 2025 10:59:04 -0800
Patch series "Cleanup for memfd_create()", v3.
memfd_create() handles all of its logic in a single function. Some of the
logic in the function is also somewhat contrived (i.e. copying the memfd
name from userpace).
This series aims to cleanup memfd_create() by splitting out the logic into
helper functions, and simplifying the memfd name copying to make the code
easier to follow.
This has no intended functional changes.
This patch (of 2):
memfd_create() is a pretty busy function that could be easier to read if
some of the logic was split out into helper functions.
Therefore, split the flags sanitization, name allocation, and file
structure allocation into their own helper functions.
No functional change.
Link: https://lkml.kernel.org/r/20250109185908.1006310-1-isaacmanjarres@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20250109185908.1006310-2-isaacmanjarres@xxxxxxxxxx
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@xxxxxxxxxx>
Cc: Alice Ryhl <aliceryhl@xxxxxxxxxx>
Cc: John Stultz <jstultz@xxxxxxxxxx>
Cc: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Jeff Xu <jeffxu@xxxxxxxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memfd.c | 82 ++++++++++++++++++++++++++++++++++++---------------
1 file changed, 59 insertions(+), 23 deletions(-)
--- a/mm/memfd.c~mm-memfd-refactor-and-cleanup-the-logic-in-memfd_create
+++ a/mm/memfd.c
@@ -369,15 +369,9 @@ int memfd_check_seals_mmap(struct file *
return err;
}
-SYSCALL_DEFINE2(memfd_create,
- const char __user *, uname,
- unsigned int, flags)
+static int sanitize_flags(unsigned int *flags_ptr)
{
- unsigned int *file_seals;
- struct file *file;
- int fd, error;
- char *name;
- long len;
+ unsigned int flags = *flags_ptr;
if (!(flags & MFD_HUGETLB)) {
if (flags & ~(unsigned int)MFD_ALL_FLAGS)
@@ -393,20 +387,25 @@ SYSCALL_DEFINE2(memfd_create,
if ((flags & MFD_EXEC) && (flags & MFD_NOEXEC_SEAL))
return -EINVAL;
- error = check_sysctl_memfd_noexec(&flags);
- if (error < 0)
- return error;
+ return check_sysctl_memfd_noexec(flags_ptr);
+}
+
+static char *alloc_name(const char __user *uname)
+{
+ int error;
+ char *name;
+ long len;
/* length includes terminating zero */
len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
if (len <= 0)
- return -EFAULT;
+ return ERR_PTR(-EFAULT);
if (len > MFD_NAME_MAX_LEN + 1)
- return -EINVAL;
+ return ERR_PTR(-EINVAL);
name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_KERNEL);
if (!name)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
strcpy(name, MFD_NAME_PREFIX);
if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
@@ -420,23 +419,28 @@ SYSCALL_DEFINE2(memfd_create,
goto err_name;
}
- fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
- if (fd < 0) {
- error = fd;
- goto err_name;
- }
+ return name;
+
+err_name:
+ kfree(name);
+ return ERR_PTR(error);
+}
+
+static struct file *alloc_file(const char *name, unsigned int flags)
+{
+ unsigned int *file_seals;
+ struct file *file;
if (flags & MFD_HUGETLB) {
file = hugetlb_file_setup(name, 0, VM_NORESERVE,
HUGETLB_ANONHUGE_INODE,
(flags >> MFD_HUGE_SHIFT) &
MFD_HUGE_MASK);
- } else
+ } else {
file = shmem_file_setup(name, 0, VM_NORESERVE);
- if (IS_ERR(file)) {
- error = PTR_ERR(file);
- goto err_fd;
}
+ if (IS_ERR(file))
+ return file;
file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
file->f_flags |= O_LARGEFILE;
@@ -456,7 +460,39 @@ SYSCALL_DEFINE2(memfd_create,
*file_seals &= ~F_SEAL_SEAL;
}
+ return file;
+}
+
+SYSCALL_DEFINE2(memfd_create,
+ const char __user *, uname,
+ unsigned int, flags)
+{
+ struct file *file;
+ int fd, error;
+ char *name;
+
+ error = sanitize_flags(&flags);
+ if (error < 0)
+ return error;
+
+ name = alloc_name(uname);
+ if (IS_ERR(name))
+ return PTR_ERR(name);
+
+ fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
+ if (fd < 0) {
+ error = fd;
+ goto err_name;
+ }
+
+ file = alloc_file(name, flags);
+ if (IS_ERR(file)) {
+ error = PTR_ERR(file);
+ goto err_fd;
+ }
+
fd_install(fd, file);
+ /* name is not needed beyond this point. */
kfree(name);
return fd;
_
Patches currently in -mm which might be from isaacmanjarres@xxxxxxxxxx are
mm-memfd-refactor-and-cleanup-the-logic-in-memfd_create.patch
mm-memfd-use-strncpy_from_user-to-read-memfd-name.patch
