From c26958cb5a0d9053d1358258827638773f3d36ed Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Fri, 19 Feb 2021 14:59:35 +0800 Subject: [PATCH] Take mmap lock in cacheflush syscall 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 Signed-off-by: Ley Foon Tan --- arch/nios2/kernel/sys_nios2.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/nios2/kernel/sys_nios2.c b/arch/nios2/kernel/sys_nios2.c index cd390ec4..b1ca856 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 +35,22 @@ 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(mm); return -EFAULT; + } flush_cache_range(vma, addr, addr + len); + mmap_read_unlock(mm); return 0; } -- 2.7.4