Changes

As 32-bit application is restored from 64-bit CRIU, some task's properties that were filled on <code>exec()</code> are left, which is quite unusual for 32-bit task. One of the things, left from 64-bit binary is precalculated <code>mmap_base</code> which is used to find task's top/bottom address limit during <code>mmap()</code> syscall. That means that compat <code>sys_mmap()</code> may map page over 4Gb address and return 4-byte pointer to low bytes of address. Looks like no one has used compatible mmap in 64-bit binary. Results in broken mmap in restored 32-bit application, which can map vma over 4Gb.

As 32-bit application is restored from 64-bit CRIU, some task's properties that were filled on <code>exec()</code> are left, which is quite unusual for 32-bit task. One of the things, left from 64-bit binary is precalculated <code>mmap_base</code> which is used to find task's top/bottom address limit during <code>mmap()</code> syscall. That means that compat <code>sys_mmap()</code> may map page over 4Gb address and return 4-byte pointer to low bytes of address. Looks like no one has used compatible mmap in 64-bit binary. Results in broken mmap in restored 32-bit application, which can map vma over 4Gb.

Patches to fix this bug at this moment were posted on lkml, but not yet accepted. See [[Upstream kernel commits]]. If they will not go to v4.9-stable, the kerndat test for 32-bit C/R will be reworked to check if the bug present in kernel (which is not nice thing, but ok).

See [[Upstream kernel commits]]. The kerndat test for 32-bit C/R will be reworked to check if the bug present in kernel (which is not nice thing, but ok).

 

Hard to reproduce.

=== List of failed tests ===

=== List of failed tests ===