x86/debug: Prevent data breakpoints on cpu_dr7

local_db_save() is called at the start of exc_debug_kernel(), reads DR7 and
disables breakpoints to prevent recursion.

When running in a guest (X86_FEATURE_HYPERVISOR), local_db_save() reads the
per-cpu variable cpu_dr7 to check whether a breakpoint is active or not
before it accesses DR7.

A data breakpoint on cpu_dr7 therefore results in infinite #DB recursion.

Disallow data breakpoints on cpu_dr7 to prevent that.

Fixes: 84b6a3491567a("x86/entry: Optimize local_db_save() for virt")
Signed-off-by: Lai Jiangshan <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]

0 files changed, 0 insertions, 0 deletions