We need to take the mmap lock around find_vma() and subsequent use of the
VMA. Otherwise, we can race with concurrent operations like munmap(), which
can lead to use-after-free accesses to freed VMAs.
Fixes: 1000197d8013 ("nios2: System calls handling")
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
---
To the maintainers:
I can't easily test this patch - I don't even have a nios2 compiler.
If you have tested this patch, you may want to add a CC stable tag to this.
arch/nios2/kernel/sys_nios2.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/nios2/kernel/sys_nios2.c b/arch/nios2/kernel/sys_nios2.c
index cd390ec4f88b..2c8f8bd850c9 100644
--- a/arch/nios2/kernel/sys_nios2.c
+++ b/arch/nios2/kernel/sys_nios2.c
@@ -22,6 +22,7 @@ asmlinkage int sys_cacheflush(unsigned long addr,
unsigned long len,
unsigned int op)
{
struct vm_area_struct *vma;
+ struct mm_struct *mm = current->mm;
if (len == 0)
return 0;
@@ -34,16 +35,21 @@ asmlinkage int sys_cacheflush(unsigned long addr,
unsigned long len,
if (addr + len < addr)
return -EFAULT;
+ if (mmap_read_lock_killable(mm))
+ return -EINTR;
/*
* Verify that the specified address region actually belongs
* to this process.
*/
- vma = find_vma(current->mm, addr);
- if (vma == NULL || addr < vma->vm_start || addr + len > vma->vm_end)
+ vma = find_vma(mm, addr);
+ if (vma == NULL || addr < vma->vm_start || addr + len > vma->vm_end) {
+ mmap_read_unlock();
return -EFAULT;
+ }
flush_cache_range(vma, addr, addr + len);
+ mmap_read_unlock();
return 0;
}
base-commit: 6d28cf7dfede6cfca5119a0d415a6a447c68f3a0
--
2.28.0.681.g6f77f65b4e-goog
