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authorAndy Lutomirski <luto@amacapital.net>2012-07-05 16:00:11 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-07-16 09:04:43 -0700
commit0c4ad5cc8c01f62fe5211b5ce9563c27f795a4ab (patch)
treea387acf3d19362ad7812134b3fdff5eb81f92c4a /mm
parentc9bb51fb8c7a9d8b230c0bd184d9af919350383b (diff)
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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") 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: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.2: - Adjust context - madvise_remove() calls vmtruncate_range(), not do_fallocate()] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/madvise.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/madvise.c b/mm/madvise.c
index 1ccbba5b667..55f645c85a3 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
@@ -203,14 +204,16 @@ 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;
}
@@ -224,9 +227,16 @@ 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 */
+ /*
+ * vmtruncate_range may need to take i_mutex. 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(&current->mm->mmap_sem);
error = vmtruncate_range(mapping->host, offset, endoff);
+ fput(f);
down_read(&current->mm->mmap_sem);
return error;
}