diff options
Diffstat (limited to 'meta/recipes-devtools/qemu/qemu/CVE-2020-24165.patch')
| -rw-r--r-- | meta/recipes-devtools/qemu/qemu/CVE-2020-24165.patch | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/meta/recipes-devtools/qemu/qemu/CVE-2020-24165.patch b/meta/recipes-devtools/qemu/qemu/CVE-2020-24165.patch new file mode 100644 index 0000000000..e0a27331a8 --- /dev/null +++ b/meta/recipes-devtools/qemu/qemu/CVE-2020-24165.patch @@ -0,0 +1,94 @@ +CVE: CVE-2020-24165 +Upstream-Status: Backport [https://github.com/qemu/qemu/commit/886cc68943ebe8cf7e5f970be33459f95068a441 ] +Signed-off-by: Lee Chee Yang <chee.yang.lee@intel.com> + +From 886cc68943ebe8cf7e5f970be33459f95068a441 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Alex=20Benn=C3=A9e?= <alex.bennee@linaro.org> +Date: Fri, 14 Feb 2020 14:49:52 +0000 +Subject: [PATCH] accel/tcg: fix race in cpu_exec_step_atomic (bug 1863025) +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +The bug describes a race whereby cpu_exec_step_atomic can acquire a TB +which is invalidated by a tb_flush before we execute it. This doesn't +affect the other cpu_exec modes as a tb_flush by it's nature can only +occur on a quiescent system. The race was described as: + + B2. tcg_cpu_exec => cpu_exec => tb_find => tb_gen_code + B3. tcg_tb_alloc obtains a new TB + + C3. TB obtained with tb_lookup__cpu_state or tb_gen_code + (same TB as B2) + + A3. start_exclusive critical section entered + A4. do_tb_flush is called, TB memory freed/re-allocated + A5. end_exclusive exits critical section + + B2. tcg_cpu_exec => cpu_exec => tb_find => tb_gen_code + B3. tcg_tb_alloc reallocates TB from B2 + + C4. start_exclusive critical section entered + C5. cpu_tb_exec executes the TB code that was free in A4 + +The simplest fix is to widen the exclusive period to include the TB +lookup. As a result we can drop the complication of checking we are in +the exclusive region before we end it. + +Cc: Yifan <me@yifanlu.com> +Buglink: https://bugs.launchpad.net/qemu/+bug/1863025 +Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> +Reviewed-by: Richard Henderson <richard.henderson@linaro.org> +Signed-off-by: Alex Bennée <alex.bennee@linaro.org> +Message-Id: <20200214144952.15502-1-alex.bennee@linaro.org> +Signed-off-by: Richard Henderson <richard.henderson@linaro.org> +--- + accel/tcg/cpu-exec.c | 21 +++++++++++---------- + 1 file changed, 11 insertions(+), 10 deletions(-) + +diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c +index 2560c90eec79..d95c4848a47b 100644 +--- a/accel/tcg/cpu-exec.c ++++ b/accel/tcg/cpu-exec.c +@@ -240,6 +240,8 @@ void cpu_exec_step_atomic(CPUState *cpu) + uint32_t cf_mask = cflags & CF_HASH_MASK; + + if (sigsetjmp(cpu->jmp_env, 0) == 0) { ++ start_exclusive(); ++ + tb = tb_lookup__cpu_state(cpu, &pc, &cs_base, &flags, cf_mask); + if (tb == NULL) { + mmap_lock(); +@@ -247,8 +249,6 @@ void cpu_exec_step_atomic(CPUState *cpu) + mmap_unlock(); + } + +- start_exclusive(); +- + /* Since we got here, we know that parallel_cpus must be true. */ + parallel_cpus = false; + cc->cpu_exec_enter(cpu); +@@ -271,14 +271,15 @@ void cpu_exec_step_atomic(CPUState *cpu) + qemu_plugin_disable_mem_helpers(cpu); + } + +- if (cpu_in_exclusive_context(cpu)) { +- /* We might longjump out of either the codegen or the +- * execution, so must make sure we only end the exclusive +- * region if we started it. +- */ +- parallel_cpus = true; +- end_exclusive(); +- } ++ ++ /* ++ * As we start the exclusive region before codegen we must still ++ * be in the region if we longjump out of either the codegen or ++ * the execution. ++ */ ++ g_assert(cpu_in_exclusive_context(cpu)); ++ parallel_cpus = true; ++ end_exclusive(); + } + + struct tb_desc { |