x86/entry/32: Use %ss segment where required

x86/entry/32: Use %ss segment where required

commit 4c4fd55d3d59a41ddfa6ecba7e76928921759f43 upstream.

When re-building the IRET frame we use %eax as an destination %esp,
make sure to then also match the segment for when there is a nonzero
SS base (ESPFIX).

[peterz: Changelog and minor edits]
Fixes: 3c88c692c287 ("x86/stackframe/32: Provide consistent pt_regs")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>