[RFC PATCH v2 7/8] mseal:Check seal flag for mmap(2)
From: jeffxu
Date: Tue Oct 17 2023 - 05:09:05 EST
From: Jeff Xu <jeffxu@xxxxxxxxxx>
mmap(2) can change a protection of existing VMAs.
Sealing will prevent unintended mmap(2) call.
What this patch does:
When a mmap(2) is invoked, if one of its VMAs has MM_SEAL_MMAP set
from previous mseal(2) call, the mmap(2) will fail, without any
VMAs modified.
The patch is based on following:
There are two cases: with MMU, NO MMU.
For MMU case:
1. ksys_mmap_pgoff() currently are called in 2 places:
SYSCALL_DEFINE1(old_mmap, ...)
SYSCALL_DEFINE6(mmap_pgoff,...)
Since both are syscall entry point, omit adding
checkSeals in the signature of ksys_mmap_pgoff().
2. ksys_mmap_pgoff() calls vm_mmap_pgoff() with
checkSeals = MM_SEAL_MMAP, in turn, checkSeals flag is
passed into do_mmap(),
Note: Of all the call paths that goes into do_mmap(),
ksys_mmap_pgoff() is the only place where
checkSeals = MM_SEAL_MMAP. The rest has checkSeals = 0.
3. In do_mmap(), call can_modify_mm() before any update
is maded to the VMAs.
For NON-MMU case:
Set checkSeals = 0 for all cases.
Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxx>
---
fs/aio.c | 5 +++--
include/linux/mm.h | 5 ++++-
ipc/shm.c | 3 ++-
mm/internal.h | 4 ++--
mm/mmap.c | 22 ++++++++++++++++++----
mm/nommu.c | 6 ++++--
mm/util.c | 8 +++++---
7 files changed, 38 insertions(+), 15 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index b3174da80ff6..7f4863d0082d 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -557,8 +557,9 @@ static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
}
ctx->mmap_base = do_mmap(ctx->aio_ring_file, 0, ctx->mmap_size,
- PROT_READ | PROT_WRITE,
- MAP_SHARED, 0, &unused, NULL);
+ PROT_READ | PROT_WRITE, MAP_SHARED, 0, &unused,
+ NULL, 0);
+
mmap_write_unlock(mm);
if (IS_ERR((void *)ctx->mmap_base)) {
ctx->mmap_size = 0;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f2f316522f2a..9f496c9f2970 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3274,9 +3274,12 @@ extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned lo
extern unsigned long mmap_region(struct file *file, unsigned long addr,
unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
struct list_head *uf);
+
extern unsigned long do_mmap(struct file *file, unsigned long addr,
unsigned long len, unsigned long prot, unsigned long flags,
- unsigned long pgoff, unsigned long *populate, struct list_head *uf);
+ unsigned long pgoff, unsigned long *populate, struct list_head *uf,
+ unsigned long checkSeals);
+
extern int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
unsigned long start, size_t len, struct list_head *uf,
bool unlock, unsigned long checkSeals);
diff --git a/ipc/shm.c b/ipc/shm.c
index 60e45e7045d4..3660f522ecba 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -1662,7 +1662,8 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg,
goto invalid;
}
- addr = do_mmap(file, addr, size, prot, flags, 0, &populate, NULL);
+ addr = do_mmap(file, addr, size, prot, flags, 0, &populate, NULL,
+ 0);
*raddr = addr;
err = 0;
if (IS_ERR_VALUE(addr))
diff --git a/mm/internal.h b/mm/internal.h
index d1d4bf4e63c0..2c074d8c6abd 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -800,8 +800,8 @@ extern u64 hwpoison_filter_memcg;
extern u32 hwpoison_filter_enable;
extern unsigned long __must_check vm_mmap_pgoff(struct file *, unsigned long,
- unsigned long, unsigned long,
- unsigned long, unsigned long);
+ unsigned long, unsigned long, unsigned long, unsigned long,
+ unsigned long checkSeals);
extern void set_pageblock_order(void);
unsigned long reclaim_pages(struct list_head *folio_list);
diff --git a/mm/mmap.c b/mm/mmap.c
index 62d592f16f45..edcadd2bb394 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1197,7 +1197,8 @@ static inline bool file_mmap_ok(struct file *file, struct inode *inode,
unsigned long do_mmap(struct file *file, unsigned long addr,
unsigned long len, unsigned long prot,
unsigned long flags, unsigned long pgoff,
- unsigned long *populate, struct list_head *uf)
+ unsigned long *populate, struct list_head *uf,
+ unsigned long checkSeals)
{
struct mm_struct *mm = current->mm;
vm_flags_t vm_flags;
@@ -1365,6 +1366,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
vm_flags |= VM_NORESERVE;
}
+ if (!can_modify_mm(mm, addr, addr + len, MM_SEAL_MMAP))
+ return -EACCES;
+
addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
if (!IS_ERR_VALUE(addr) &&
((vm_flags & VM_LOCKED) ||
@@ -1411,7 +1415,17 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
return PTR_ERR(file);
}
- retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
+ /*
+ * vm_mmap_pgoff() currently called from two places:
+ * SYSCALL_DEFINE1(old_mmap, ...)
+ * SYSCALL_DEFINE6(mmap_pgoff,...)
+ * and not in any other places.
+ * Therefore, omit changing the signature of vm_mmap_pgoff()
+ * Otherwise, we might need to add checkSeals and pass it
+ * from all callers of vm_mmap_pgoff().
+ */
+ retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff,
+ MM_SEAL_MMAP);
out_fput:
if (file)
fput(file);
@@ -3016,8 +3030,8 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
flags |= MAP_LOCKED;
file = get_file(vma->vm_file);
- ret = do_mmap(vma->vm_file, start, size,
- prot, flags, pgoff, &populate, NULL);
+ ret = do_mmap(vma->vm_file, start, size, prot, flags, pgoff,
+ &populate, NULL, 0);
fput(file);
out:
mmap_write_unlock(mm);
diff --git a/mm/nommu.c b/mm/nommu.c
index 8dba41cfc44d..dc83651ee777 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1018,7 +1018,8 @@ unsigned long do_mmap(struct file *file,
unsigned long flags,
unsigned long pgoff,
unsigned long *populate,
- struct list_head *uf)
+ struct list_head *uf,
+ unsigned long checkSeals)
{
struct vm_area_struct *vma;
struct vm_region *region;
@@ -1262,7 +1263,8 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
goto out;
}
- retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
+ retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff,
+ 0);
if (file)
fput(file);
diff --git a/mm/util.c b/mm/util.c
index 4ed8b9b5273c..ca9d8c69267c 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -532,7 +532,8 @@ EXPORT_SYMBOL_GPL(account_locked_vm);
unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
unsigned long len, unsigned long prot,
- unsigned long flag, unsigned long pgoff)
+ unsigned long flag, unsigned long pgoff,
+ unsigned long checkseals)
{
unsigned long ret;
struct mm_struct *mm = current->mm;
@@ -544,7 +545,7 @@ unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
if (mmap_write_lock_killable(mm))
return -EINTR;
ret = do_mmap(file, addr, len, prot, flag, pgoff, &populate,
- &uf);
+ &uf, checkseals);
mmap_write_unlock(mm);
userfaultfd_unmap_complete(mm, &uf);
if (populate)
@@ -562,7 +563,8 @@ unsigned long vm_mmap(struct file *file, unsigned long addr,
if (unlikely(offset_in_page(offset)))
return -EINVAL;
- return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
+ return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT,
+ 0);
}
EXPORT_SYMBOL(vm_mmap);
--
2.42.0.655.g421f12c284-goog