diff options
Diffstat (limited to 'system/xen/xsa/xsa260-4.patch')
| -rw-r--r-- | system/xen/xsa/xsa260-4.patch | 72 |
1 files changed, 0 insertions, 72 deletions
diff --git a/system/xen/xsa/xsa260-4.patch b/system/xen/xsa/xsa260-4.patch deleted file mode 100644 index c2fa02d6e1..0000000000 --- a/system/xen/xsa/xsa260-4.patch +++ /dev/null @@ -1,72 +0,0 @@ -From: Andrew Cooper <andrew.cooper3@citrix.com> -Subject: x86/traps: Fix handling of #DB exceptions in hypervisor context - -The WARN_ON() can be triggered by guest activities, and emits a full stack -trace without rate limiting. Swap it out for a ratelimited printk with just -enough information to work out what is going on. - -Not all #DB exceptions are traps, so blindly continuing is not a safe action -to take. We don't let PV guests select these settings in the real %dr7 to -begin with, but for added safety against unexpected situations, detect the -fault cases and crash in an obvious manner. - -This is part of XSA-260 / CVE-2018-8897. - -Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> -Reviewed-by: Jan Beulich <jbeulich@suse.com> - ---- a/xen/arch/x86/traps.c -+++ b/xen/arch/x86/traps.c -@@ -1809,16 +1809,44 @@ void do_debug(struct cpu_user_regs *regs - regs->eflags &= ~X86_EFLAGS_TF; - } - } -- else -+ -+ /* -+ * Check for fault conditions. General Detect, and instruction -+ * breakpoints are faults rather than traps, at which point attempting -+ * to ignore and continue will result in a livelock. -+ */ -+ if ( dr6 & DR_GENERAL_DETECT ) -+ { -+ printk(XENLOG_ERR "Hit General Detect in Xen context\n"); -+ fatal_trap(regs, 0); -+ } -+ -+ if ( dr6 & (DR_TRAP3 | DR_TRAP2 | DR_TRAP1 | DR_TRAP0) ) - { -- /* -- * We ignore watchpoints when they trigger within Xen. This may -- * happen when a buffer is passed to us which previously had a -- * watchpoint set on it. No need to bump EIP; the only faulting -- * trap is an instruction breakpoint, which can't happen to us. -- */ -- WARN_ON(!search_exception_table(regs)); -+ unsigned int bp, dr7 = read_debugreg(7) >> DR_CONTROL_SHIFT; -+ -+ for ( bp = 0; bp < 4; ++bp ) -+ { -+ if ( (dr6 & (1u << bp)) && /* Breakpoint triggered? */ -+ ((dr7 & (3u << (bp * DR_CONTROL_SIZE))) == 0) /* Insn? */ ) -+ { -+ printk(XENLOG_ERR -+ "Hit instruction breakpoint in Xen context\n"); -+ fatal_trap(regs, 0); -+ } -+ } - } -+ -+ /* -+ * Whatever caused this #DB should be a trap. Note it and continue. -+ * Guests can trigger this in certain corner cases, so ensure the -+ * message is ratelimited. -+ */ -+ gprintk(XENLOG_WARNING, -+ "Hit #DB in Xen context: %04x:%p [%ps], stk %04x:%p, dr6 %lx\n", -+ regs->cs, _p(regs->rip), _p(regs->rip), -+ regs->ss, _p(regs->rsp), dr6); -+ - goto out; - } - |