powerpc/vdso: Fix VDSO data access when running in a non-root time namespace

When running in a non-root time namespace, the global VDSO data page
is replaced by a dedicated namespace data page and the global data
page is mapped next to it. Detailed explanations can be found at
commit 660fd04f9317 ("lib/vdso: Prepare for time namespace support").

When it happens, __kernel_get_syscall_map and __kernel_get_tbfreq
and __kernel_sync_dicache don't work anymore because they read 0
instead of the data they need.

To address that, clock_mode has to be read. When it is set to
VDSO_CLOCKMODE_TIMENS, it means it is a dedicated namespace data page
and the global data is located on the following page.

Add a macro called get_realdatapage which reads clock_mode and add
PAGE_SIZE to the pointer provided by get_datapage macro when
clock_mode is equal to VDSO_CLOCKMODE_TIMENS. Use this new macro
instead of get_datapage macro except for time functions as they handle
it internally.

Fixes: 74205b3fc2ef ("powerpc/vdso: Add support for time namespaces")
Reported-by: Jason A. Donenfeld <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Christophe Leroy <[email protected]>
Acked-by: Michael Ellerman <[email protected]>
Signed-off-by: Jason A. Donenfeld <[email protected]>

0 files changed, 0 insertions, 0 deletions