| From c995b72bc4c090d03944f919d137b205eac43a64 Mon Sep 17 00:00:00 2001 |
| From: Andy Lutomirski <luto@amacapital.net> |
| Date: Thu, 5 Jul 2012 16:00:11 -0700 |
| Subject: [PATCH] mm: Hold a file reference in madvise_remove |
| |
| commit 9ab4233dd08036fe34a89c7dc6f47a8bf2eb29eb upstream. |
| |
| Otherwise the code races with munmap (causing a use-after-free |
| of the vma) or with close (causing a use-after-free of the struct |
| file). |
| |
| The bug was introduced by commit 90ed52ebe481 ("[PATCH] holepunch: fix |
| mmap_sem i_mutex deadlock") |
| |
| [bwh: Backported to 3.2: |
| - Adjust context |
| - madvise_remove() calls vmtruncate_range(), not do_fallocate()] |
| [luto: Backported to 3.0: Adjust context] |
| |
| Cc: Hugh Dickins <hugh@veritas.com> |
| Cc: Miklos Szeredi <mszeredi@suse.cz> |
| Cc: Badari Pulavarty <pbadari@us.ibm.com> |
| Cc: Nick Piggin <npiggin@suse.de> |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| Signed-off-by: Andy Lutomirski <luto@amacapital.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| [PG: commit e12fcd38abe8a869cbabd77724008f1cf812a3e7 in v3.0.37] |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| --- |
| mm/madvise.c | 16 +++++++++++++--- |
| 1 file changed, 13 insertions(+), 3 deletions(-) |
| |
| diff --git a/mm/madvise.c b/mm/madvise.c |
| index 319528b8db74..83aa92aad8bc 100644 |
| --- a/mm/madvise.c |
| +++ b/mm/madvise.c |
| @@ -13,6 +13,7 @@ |
| #include <linux/hugetlb.h> |
| #include <linux/sched.h> |
| #include <linux/ksm.h> |
| +#include <linux/file.h> |
| |
| /* |
| * Any behaviour which results in changes to the vma->vm_flags needs to |
| @@ -191,14 +192,16 @@ static long madvise_remove(struct vm_area_struct *vma, |
| struct address_space *mapping; |
| loff_t offset, endoff; |
| int error; |
| + struct file *f; |
| |
| *prev = NULL; /* tell sys_madvise we drop mmap_sem */ |
| |
| if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB)) |
| return -EINVAL; |
| |
| - if (!vma->vm_file || !vma->vm_file->f_mapping |
| - || !vma->vm_file->f_mapping->host) { |
| + f = vma->vm_file; |
| + |
| + if (!f || !f->f_mapping || !f->f_mapping->host) { |
| return -EINVAL; |
| } |
| |
| @@ -212,9 +215,16 @@ static long madvise_remove(struct vm_area_struct *vma, |
| endoff = (loff_t)(end - vma->vm_start - 1) |
| + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); |
| |
| - /* vmtruncate_range needs to take i_mutex and i_alloc_sem */ |
| + /* |
| + * vmtruncate_range may need to take i_mutex and i_alloc_sem. |
| + * We need to explicitly grab a reference because the vma (and |
| + * hence the vma's reference to the file) can go away as soon as |
| + * we drop mmap_sem. |
| + */ |
| + get_file(f); |
| up_read(¤t->mm->mmap_sem); |
| error = vmtruncate_range(mapping->host, offset, endoff); |
| + fput(f); |
| down_read(¤t->mm->mmap_sem); |
| return error; |
| } |
| -- |
| 1.8.5.2 |
| |