nick,
On Tue, Feb 20, 2007 at 03:18:56PM +0100, Nick Piggin wrote:
> From: Nick Piggin <[EMAIL PROTECTED]>
>
> Perfmon associates vmalloc()ed memory with a file descriptor, and installs
> a vma mapping that memory. Unfortunately, the vm_file field is not filled in,
> so processes with mappings to that memory do not prevent the file from being
> closed and the memory freed. This results in use-after-free bugs and multiple
> freeing of pages, etc.
>
> I saw this bug on an Altix on SLES9. Haven't reproduced upstream but it looks
> like the same issue is there.
>
I think this is possible for the old perfmon v2.0 codebase that is currently in
mainline for IA-64. I have corrected this with the multi-arch v2.3 code base
available as a kernel patch for the moment.
Thanks.
> Signed-off-by: Nick Piggin <[EMAIL PROTECTED]>
>
> Index: linux-2.6/arch/ia64/kernel/perfmon.c
> ===================================================================
> --- linux-2.6.orig/arch/ia64/kernel/perfmon.c
> +++ linux-2.6/arch/ia64/kernel/perfmon.c
> @@ -2261,7 +2261,7 @@ pfm_remap_buffer(struct vm_area_struct *
> * allocate a sampling buffer and remaps it into the user address space of
> the task
> */
> static int
> -pfm_smpl_buffer_alloc(struct task_struct *task, pfm_context_t *ctx, unsigned
> long rsize, void **user_vaddr)
> +pfm_smpl_buffer_alloc(struct task_struct *task, struct file *filp,
> pfm_context_t *ctx, unsigned long rsize, void **user_vaddr)
> {
> struct mm_struct *mm = task->mm;
> struct vm_area_struct *vma = NULL;
> @@ -2312,6 +2312,7 @@ pfm_smpl_buffer_alloc(struct task_struct
> * partially initialize the vma for the sampling buffer
> */
> vma->vm_mm = mm;
> + vma->vm_file = filp;
> vma->vm_flags = VM_READ| VM_MAYREAD |VM_RESERVED;
> vma->vm_page_prot = PAGE_READONLY; /* XXX may need to change */
>
> @@ -2350,6 +2351,8 @@ pfm_smpl_buffer_alloc(struct task_struct
> goto error;
> }
>
> + get_file(filp);
> +
> /*
> * now insert the vma in the vm list for the process, must be
> * done with mmap lock held
> @@ -2427,7 +2430,7 @@ pfarg_is_sane(struct task_struct *task,
> }
>
> static int
> -pfm_setup_buffer_fmt(struct task_struct *task, pfm_context_t *ctx, unsigned
> int ctx_flags,
> +pfm_setup_buffer_fmt(struct task_struct *task, struct file *filp,
> pfm_context_t *ctx, unsigned int ctx_flags,
> unsigned int cpu, pfarg_context_t *arg)
> {
> pfm_buffer_fmt_t *fmt = NULL;
> @@ -2468,7 +2471,7 @@ pfm_setup_buffer_fmt(struct task_struct
> /*
> * buffer is always remapped into the caller's address space
> */
> - ret = pfm_smpl_buffer_alloc(current, ctx, size, &uaddr);
> + ret = pfm_smpl_buffer_alloc(current, filp, ctx, size, &uaddr);
> if (ret) goto error;
>
> /* keep track of user address of buffer */
> @@ -2679,7 +2682,7 @@ pfm_context_create(pfm_context_t *ctx, v
> * does the user want to sample?
> */
> if (pfm_uuid_cmp(req->ctx_smpl_buf_id, pfm_null_uuid)) {
> - ret = pfm_setup_buffer_fmt(current, ctx, ctx_flags, 0, req);
> + ret = pfm_setup_buffer_fmt(current, filp, ctx, ctx_flags, 0,
> req);
> if (ret) goto buffer_error;
> }
>
--
-Stephane
-
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