| Message ID | 1346340168-13685-1-git-send-email-tim.gardner@canonical.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Aug 30, 2012 at 09:22:48AM -0600, Tim Gardner wrote: > @@ -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 */ > + /* > + * Filesystem's fallocate may need to take i_mutex. We need to Just a minor nit here: for older versions it's still vmtruncate_range, so perhaps the comment could be kept as: "vmtruncate_range needs to take i_mutex and i_alloc_sem. We need to..." but it doesn't change the result, just noted this. In any case Ack on the backport. > + * 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; > } > -- > 1.7.9.5
On 08/30/2012 08:22 AM, Tim Gardner wrote: > From: Andy Lutomirski <luto@amacapital.net> > > CVE-2012-3511 > > BugLink: http://bugs.launchpad.net/bugs/1042447 > > 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> > Cc: stable@vger.kernel.org > Signed-off-by: Andy Lutomirski <luto@amacapital.net> > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> > (back ported from commit 9ab4233dd08036fe34a89c7dc6f47a8bf2eb29eb) > > Signed-off-by: Tim Gardner <tim.gardner@canonical.com> > --- > mm/madvise.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 35b1479..e51291d 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -5,6 +5,7 @@ > * Copyright (C) 2002 Christoph Hellwig > */ > > +#include <linux/file.h> > #include <linux/mman.h> > #include <linux/pagemap.h> > #include <linux/syscalls.h> > @@ -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 */ > + /* > + * Filesystem's fallocate 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; > } >
Applied, with the fix in the comment to maintain reference to old function.
diff --git a/mm/madvise.c b/mm/madvise.c index 35b1479..e51291d 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -5,6 +5,7 @@ * Copyright (C) 2002 Christoph Hellwig */ +#include <linux/file.h> #include <linux/mman.h> #include <linux/pagemap.h> #include <linux/syscalls.h> @@ -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 */ + /* + * Filesystem's fallocate 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; }