From: Lorenzo Stoakes <lstoakes@gmail.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>,
Muchun Song <muchun.song@linux.dev>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Hugh Dickins <hughd@google.com>,
Andy Lutomirski <luto@kernel.org>, Jan Kara <jack@suse.cz>,
linux-fsdevel@vger.kernel.org, bpf@vger.kernel.org,
Lorenzo Stoakes <lstoakes@gmail.com>
Subject: [PATCH v3 2/3] mm: update memfd seal write check to include F_SEAL_WRITE
Date: Sat, 7 Oct 2023 21:51:00 +0100 [thread overview]
Message-ID: <f33faf83fe231441b41a8eeb170e9212b346c547.1696709413.git.lstoakes@gmail.com> (raw)
In-Reply-To: <cover.1696709413.git.lstoakes@gmail.com>
The seal_check_future_write() function is called by shmem_mmap() or
hugetlbfs_file_mmap() to disallow any future writable mappings of an memfd
sealed this way.
The F_SEAL_WRITE flag is not checked here, as that is handled via the
mapping->i_mmap_writable mechanism and so any attempt at a mapping would
fail before this could be run.
However we intend to change this, meaning this check can be performed for
F_SEAL_WRITE mappings also.
The logic here is equally applicable to both flags, so update this function
to accommodate both and rename it accordingly.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
---
fs/hugetlbfs/inode.c | 2 +-
include/linux/mm.h | 15 ++++++++-------
mm/shmem.c | 2 +-
3 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 06693bb1153d..5c333373dcc9 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -112,7 +112,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
vm_flags_set(vma, VM_HUGETLB | VM_DONTEXPAND);
vma->vm_ops = &hugetlb_vm_ops;
- ret = seal_check_future_write(info->seals, vma);
+ ret = seal_check_write(info->seals, vma);
if (ret)
return ret;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c9e9628addc4..51a217ed4d1b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4027,25 +4027,26 @@ static inline void mem_dump_obj(void *object) {}
#endif
/**
- * seal_check_future_write - Check for F_SEAL_FUTURE_WRITE flag and handle it
+ * seal_check_write - Check for F_SEAL_WRITE or F_SEAL_FUTURE_WRITE flags and
+ * handle them.
* @seals: the seals to check
* @vma: the vma to operate on
*
- * Check whether F_SEAL_FUTURE_WRITE is set; if so, do proper check/handling on
- * the vma flags. Return 0 if check pass, or <0 for errors.
+ * Check whether F_SEAL_WRITE or F_SEAL_FUTURE_WRITE are set; if so, do proper
+ * check/handling on the vma flags. Return 0 if check pass, or <0 for errors.
*/
-static inline int seal_check_future_write(int seals, struct vm_area_struct *vma)
+static inline int seal_check_write(int seals, struct vm_area_struct *vma)
{
- if (seals & F_SEAL_FUTURE_WRITE) {
+ if (seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) {
/*
* New PROT_WRITE and MAP_SHARED mmaps are not allowed when
- * "future write" seal active.
+ * write seals are active.
*/
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_WRITE))
return -EPERM;
/*
- * Since an F_SEAL_FUTURE_WRITE sealed memfd can be mapped as
+ * Since an F_SEAL_[FUTURE_]WRITE sealed memfd can be mapped as
* MAP_SHARED and read-only, take care to not allow mprotect to
* revert protections on such mappings. Do this only for shared
* mappings. For private mappings, don't need to mask
diff --git a/mm/shmem.c b/mm/shmem.c
index 6503910b0f54..cab053831fea 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2405,7 +2405,7 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
struct shmem_inode_info *info = SHMEM_I(inode);
int ret;
- ret = seal_check_future_write(info->seals, vma);
+ ret = seal_check_write(info->seals, vma);
if (ret)
return ret;
--
2.42.0
next prev parent reply other threads:[~2023-10-07 20:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-07 20:50 [PATCH v3 0/3] permit write-sealed memfd read-only shared mappings Lorenzo Stoakes
2023-10-07 20:50 ` [PATCH v3 1/3] mm: drop the assumption that VM_SHARED always implies writable Lorenzo Stoakes
2023-10-07 20:51 ` Lorenzo Stoakes [this message]
2023-10-07 20:51 ` [PATCH v3 3/3] mm: enforce the mapping_map_writable() check after call_mmap() Lorenzo Stoakes
2023-10-11 9:46 ` Jan Kara
2023-10-11 18:14 ` Lorenzo Stoakes
2023-10-12 8:38 ` Jan Kara
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f33faf83fe231441b41a8eeb170e9212b346c547.1696709413.git.lstoakes@gmail.com \
--to=lstoakes@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=bpf@vger.kernel.org \
--cc=brauner@kernel.org \
--cc=hughd@google.com \
--cc=jack@suse.cz \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mike.kravetz@oracle.com \
--cc=muchun.song@linux.dev \
--cc=viro@zeniv.linux.org.uk \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).