linux.git/mm/memfd.c, branch v6.17

mm/memfd: replace deprecated strcpy() with memcpy() in alloc_name()

2025-07-20T01:59:57+00:00

strcpy() is deprecated; use memcpy() instead.

Not copying the NUL terminator is safe because strncpy_from_user() would
overwrite it anyway by appending uname to the destination buffer at index
MFD_NAME_PREFIX_LEN.

No functional changes intended.

Link: https://github.com/KSPP/linux/issues/88
Link: https://lkml.kernel.org/r/20250712174516.64243-2-thorsten.blum@linux.dev
Signed-off-by: Thorsten Blum 
Cc: Baolin Wang 
Cc: Hugh Dickins 
Signed-off-by: Andrew Morton

mm/memfd: reserve hugetlb folios before allocation

2025-07-10T05:42:15+00:00

When we try to allocate a folio via alloc_hugetlb_folio_reserve(), we need
to ensure that there is an active reservation associated with the
allocation.  Otherwise, our allocation request would fail if there are no
active reservations made at that moment against any other allocations. 
This is because alloc_hugetlb_folio_reserve() checks h->resv_huge_pages
before proceeding with the allocation.

Therefore, to address this issue, we just need to make a reservation (by
calling hugetlb_reserve_pages()) before we try to allocate the folio. 
This will also ensure that proper region/subpool accounting is done
associated with our allocation.

Link: https://lkml.kernel.org/r/20250618053415.1036185-3-vivek.kasireddy@intel.com
Signed-off-by: Vivek Kasireddy 
Cc: Steve Sistare 
Cc: Muchun Song 
Cc: David Hildenbrand 
Cc: Gerd Hoffmann 
Cc: Oscar Salvador 
Signed-off-by: Andrew Morton

mm: update core kernel code to use vm_flags_t consistently

2025-07-10T05:42:13+00:00

The core kernel code is currently very inconsistent in its use of
vm_flags_t vs.  unsigned long.  This prevents us from changing the type of
vm_flags_t in the future and is simply not correct, so correct this.

While this results in rather a lot of churn, it is a critical
pre-requisite for a future planned change to VMA flag type.

Additionally, update VMA userland tests to account for the changes.

To make review easier and to break things into smaller parts, driver and
architecture-specific changes is left for a subsequent commit.

The code has been adjusted to cascade the changes across all calling code
as far as is needed.

We will adjust architecture-specific and driver code in a subsequent patch.

Overall, this patch does not introduce any functional change.

Link: https://lkml.kernel.org/r/d1588e7bb96d1ea3fe7b9df2c699d5b4592d901d.1750274467.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes 
Acked-by: Kees Cook 
Acked-by: Mike Rapoport (Microsoft) 
Acked-by: Jan Kara 
Acked-by: Christian Brauner 
Reviewed-by: Vlastimil Babka 
Acked-by: Oscar Salvador 
Reviewed-by: Pedro Falcato 
Acked-by: Zi Yan 
Acked-by: David Hildenbrand 
Reviewed-by: Anshuman Khandual 
Cc: Jann Horn 
Cc: Liam R. Howlett 
Cc: Catalin Marinas 
Cc: Jarkko Sakkinen 
Signed-off-by: Andrew Morton

mm: use folio_expected_ref_count() helper for reference counting

2025-07-10T05:42:08+00:00

Replace open-coded folio reference count calculations with the
folio_expected_ref_count().

No functional changes intended.

Link: https://lkml.kernel.org/r/20250611052706.515408-2-shivankg@amd.com
Signed-off-by: Shivank Garg 
Acked-by: David Hildenbrand 
Reviewed-by: Oscar Salvador 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Alistair Popple 
Cc: Arnaldo Carvalho de Melo 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: Jiri Olsa 
Cc: Kan Liang 
Cc: Marc Rutland 
Cc: "Masami Hiramatsu (Google)" 
Cc: Matthew Wilcox (Oracle) 
Cc: Namhyung kim 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Signed-off-by: Andrew Morton

mm/memfd: clarify error handling labels in memfd_create()

2025-07-10T05:42:05+00:00

err_name --> err_free_name (fd failure case)
err_fd --> err_free_fd (file failure case)

Link: https://lkml.kernel.org/r/20250610083730.527619-1-ye.liu@linux.dev
Signed-off-by: Ye Liu 
Signed-off-by: Andrew Morton

mm: move folio_index to mm/swap.h and remove no longer needed helper

2025-05-13T06:50:50+00:00

There are no remaining users of folio_index() outside the mm subsystem. 
Move it to mm/swap.h to co-locate it with swap_cache_index(), eliminating
a forward declaration, and a function call overhead.

Also remove the helper that was used to fix circular header dependency
issue.

Link: https://lkml.kernel.org/r/20250430181052.55698-6-ryncsn@gmail.com
Signed-off-by: Kairui Song 
Acked-by: David Hildenbrand 
Cc: Chao Yu 
Cc: Chris Li 
Cc: Chris Mason 
Cc: Christian Brauner 
Cc: David Sterba 
Cc: "Huang, Ying" 
Cc: Hugh Dickins 
Cc: Jaegeuk Kim 
Cc: Joanne Koong 
Cc: Johannes Weiner 
Cc: Josef Bacik 
Cc: Matthew Wilcox (Oracle) 
Cc: Miklos Szeredi 
Cc: Nhat Pham 
Cc: Qu Wenruo 
Cc: Yosry Ahmed 
Signed-off-by: Andrew Morton

mm/memfd: fix spelling and grammatical issues

2025-03-17T05:06:04+00:00

The comment "If a private mapping then writability is irrelevant" contains
a typo.  It should be "If a private mapping then writability is
irrelevant".  The comment "SEAL_EXEC implys SEAL_WRITE, making W^X from
the start." contains a typo.  It should be "SEAL_EXEC implies SEAL_WRITE,
making W^X from the start."

Link: https://lkml.kernel.org/r/20250206060958.98010-1-liuye@kylinos.cn
Signed-off-by: Liu Ye 
Signed-off-by: Andrew Morton

mm/memfd: use strncpy_from_user() to read memfd name

2025-01-26T04:22:40+00:00

The existing logic uses strnlen_user() to calculate the length of the
memfd name from userspace and then copies the string into a buffer using
copy_from_user().  This is error-prone, as the string length could have
changed between the time when it was calculated and when the string was
copied.  The existing logic handles this by ensuring that the last byte in
the buffer is the terminating zero.

This handling is contrived and can better be handled by using
strncpy_from_user(), which gets the length of the string and copies it in
one shot.  Therefore, simplify the logic for copying the memfd name by
using strncpy_from_user().

No functional change.

Link: https://lkml.kernel.org/r/20250110165904.3437374-3-isaacmanjarres@google.com
Signed-off-by: Isaac J. Manjarres 
Reviewed-by: Alice Ryhl 
Reviewed-by: Lorenzo Stoakes 
Cc: John Stultz 
Cc: Kalesh Singh 
Cc: Suren Baghdasaryan 
Signed-off-by: Andrew Morton

mm/memfd: refactor and cleanup the logic in memfd_create()

2025-01-26T04:22:40+00:00

Patch series "Cleanup for memfd_create()", v4.

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.

Thank you Alice and Lorenzo for reviewing v3 of this series and for your
feedback!


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/20250110165904.3437374-1-isaacmanjarres@google.com
Link: https://lkml.kernel.org/r/20250110165904.3437374-2-isaacmanjarres@google.com
Signed-off-by: Isaac J. Manjarres 
Reviewed-by: Alice Ryhl 
Reviewed-by: Lorenzo Stoakes 
Cc: Isaac J. Manjarres 
Cc: John Stultz 
Cc: Kalesh Singh 
Cc: Suren Baghdasaryan 
Signed-off-by: Andrew Morton

mm: perform all memfd seal checks in a single place

2025-01-14T06:40:51+00:00

We no longer actually need to perform these checks in the f_op->mmap()
hook any longer.

We already moved the operation which clears VM_MAYWRITE on a read-only
mapping of a write-sealed memfd in order to work around the restrictions
imposed by commit 5de195060b2e ("mm: resolve faulty mmap_region() error
path behaviour").

There is no reason for us not to simply go ahead and additionally check to
see if any pre-existing seals are in place here rather than defer this to
the f_op->mmap() hook.

By doing this we remove more logic from shmem_mmap() which doesn't belong
there, as well as doing the same for hugetlbfs_file_mmap().  We also
remove dubious shared logic in mm.h which simply does not belong there
either.

It makes sense to do these checks at the earliest opportunity, we know
these are shmem (or hugetlbfs) mappings whose relevant VMA flags will not
change from the invoking do_mmap() so there is simply no need to wait.

This also means the implementation of further memfd seal flags can be done
within mm/memfd.c and also have the opportunity to modify VMA flags as
necessary early in the mapping logic.

[lorenzo.stoakes@oracle.com: fix typos in !memfd inline stub]
  Link: https://lkml.kernel.org/r/7dee6c5d-480b-4c24-b98e-6fa47dbd8a23@lucifer.local
Link: https://lkml.kernel.org/r/20241206212846.210835-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes 
Tested-by: Isaac J. Manjarres 
Cc: Hugh Dickins 
Cc: Jann Horn 
Cc: Kalesh Singh 
Cc: Liam R. Howlett 
Cc: Muchun Song 
Cc: Vlastimil Babka 
Cc: Jeff Xu 
Signed-off-by: Andrew Morton