diff options
author | Andy Lutomirski <luto@amacapital.net> | 2012-07-05 16:00:11 -0700 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-07-16 09:04:43 -0700 |
commit | 0c4ad5cc8c01f62fe5211b5ce9563c27f795a4ab (patch) | |
tree | a387acf3d19362ad7812134b3fdff5eb81f92c4a /mm | |
parent | c9bb51fb8c7a9d8b230c0bd184d9af919350383b (diff) | |
download | lwn-0c4ad5cc8c01f62fe5211b5ce9563c27f795a4ab.tar.gz lwn-0c4ad5cc8c01f62fe5211b5ce9563c27f795a4ab.zip |
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.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/madvise.c b/mm/madvise.c index 1ccbba5b6674..55f645c85a35 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(¤t->mm->mmap_sem); error = vmtruncate_range(mapping->host, offset, endoff); + fput(f); down_read(¤t->mm->mmap_sem); return error; } |