On Sun, 10 Mar 2013 20:55:21 +0200 Tommi Rantala <tt.rantala@xxxxxxxxx> wrote: > 2012/12/21 Michel Lespinasse <walken@xxxxxxxxxx>: > > Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx> > > Hello, this patch introduced the following bug, seen while fuzzing with trinity: > > [ 396.825414] BUG: unable to handle kernel NULL pointer dereference > at 0000000000000050 > > ... > > > + vm_flags = vma->vm_flags; > > When find_vma() fails, vma is NULL here. Yup, thanks. This, methinks: From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Subject: mm/fremap.c: fix oops on error path If find_vma() fails, sys_remap_file_pages() will dereference `vma', which contains NULL. Fix it by checking the pointer. (We could alternatively check for err==0, but this seems more direct) (The vm_flags change is to squish a bogus used-uninitialised warning without adding extra code). Reported-by: Tommi Rantala <tt.rantala@xxxxxxxxx> Cc: Michel Lespinasse <walken@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/fremap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff -puN mm/fremap.c~mm-fremapc-fix-oops-on-error-path mm/fremap.c --- a/mm/fremap.c~mm-fremapc-fix-oops-on-error-path +++ a/mm/fremap.c @@ -163,7 +163,8 @@ SYSCALL_DEFINE5(remap_file_pages, unsign * and that the remapped range is valid and fully within * the single existing vma. */ - if (!vma || !(vma->vm_flags & VM_SHARED)) + vm_flags = vma->vm_flags; + if (!vma || !(vm_flags & VM_SHARED)) goto out; if (!vma->vm_ops || !vma->vm_ops->remap_pages) @@ -254,7 +255,8 @@ get_write_lock: */ out: - vm_flags = vma->vm_flags; + if (vma) + vm_flags = vma->vm_flags; if (likely(!has_write_lock)) up_read(&mm->mmap_sem); else _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>