| Date | Tue, 02 Oct 2012 00:53:33 +0200 | From | Willy Tarreau <> | Subject | [ 096/180] mm: Hold a file reference in madvise_remove |
| |
2.6.32-longterm review patch. If anyone has any objections, please let me know.
------------------
From: Andy Lutomirski <luto@amacapital.net>
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> Signed-off-by: Willy Tarreau <w@1wt.eu> --- mm/madvise.c | 16 +++++++++++++--- 1 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c index 35b1479..e405c5f 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -12,6 +12,7 @@ #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 @@ -190,14 +191,16 @@ 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; } @@ -211,9 +214,16 @@ 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; } -- 1.7.2.1.45.g54fbc
|