[CRIU] regression with 8ffbe754bd9: rst: Lock rst memory allocations earlier

[Pavel Emelyanov]

On 07/15/2015 03:42 PM, Tycho Andersen wrote:
> Hi Pavel,
> 
> I'm seeing a regression with the patch in the subject, it does this
> for a while:
> 
> (00.138425)    492: Error (rst-malloc.c:130): BUG at rst-malloc.c:130
> 
> And then eventually seg faults. Any ideas?

Well, yes :) I (unintentionally) broke this with the patch you've spotted.
Sorry about that :(

The thing is that this code

        if (lsm) {
                char *rendered;
                int ret;

                ret = render_lsm_profile(lsm, &rendered);
                xfree(lsm);
                if (ret < 0) {
                        goto err_nv;
                }

                lsm_pos = rst_mem_cpos(RM_PRIVATE);
                lsm_profile_len = strlen(rendered);
                lsm = rst_mem_alloc(lsm_profile_len + 1, RM_PRIVATE);
                if (!lsm) {
                        xfree(rendered);
                        goto err_nv;
                }

                strncpy(lsm, rendered, lsm_profile_len);
                xfree(rendered);

        }

form sigreturn_restore() extends the remapable area _after_ we've found
a hole for it in the restorer address spaces. So we're risking in having
some memory overwritten by it.

I missed this "if (lsm) ..." code when I was disabling allocations from 
remapable area (with rst_mem_alloc) after the hole is found. The fix for 
that is to move all the rst_mem_alloc() calls _before_ rst_mem_lock(), 
but I don't have LSM-enabled system to check the fix works. Can you do
it, please? :)

-- Pavel