From 4731f89b3b9690efccb6084b9fee43083669de14 Mon Sep 17 00:00:00 2001 From: Emilio Cota Date: Tue, 24 Jan 2023 18:01:18 +0000 Subject: cpu: free cpu->tb_jmp_cache with RCU MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Fixes the appended use-after-free. The root cause is that during tb invalidation we use CPU_FOREACH, and therefore to safely free a vCPU we must wait for an RCU grace period to elapse. $ x86_64-linux-user/qemu-x86_64 tests/tcg/x86_64-linux-user/munmap-pthread ================================================================= ==1800604==ERROR: AddressSanitizer: heap-use-after-free on address 0x62d0005f7418 at pc 0x5593da6704eb bp 0x7f4961a7ac70 sp 0x7f4961a7ac60 READ of size 8 at 0x62d0005f7418 thread T2 #0 0x5593da6704ea in tb_jmp_cache_inval_tb ../accel/tcg/tb-maint.c:244 #1 0x5593da6704ea in do_tb_phys_invalidate ../accel/tcg/tb-maint.c:290 #2 0x5593da670631 in tb_phys_invalidate__locked ../accel/tcg/tb-maint.c:306 #3 0x5593da670631 in tb_invalidate_phys_page_range__locked ../accel/tcg/tb-maint.c:542 #4 0x5593da67106d in tb_invalidate_phys_range ../accel/tcg/tb-maint.c:614 #5 0x5593da6a64d4 in target_munmap ../linux-user/mmap.c:766 #6 0x5593da6dba05 in do_syscall1 ../linux-user/syscall.c:10105 #7 0x5593da6f564c in do_syscall ../linux-user/syscall.c:13329 #8 0x5593da49e80c in cpu_loop ../linux-user/x86_64/../i386/cpu_loop.c:233 #9 0x5593da6be28c in clone_func ../linux-user/syscall.c:6633 #10 0x7f496231cb42 in start_thread nptl/pthread_create.c:442 #11 0x7f49623ae9ff (/lib/x86_64-linux-gnu/libc.so.6+0x1269ff) 0x62d0005f7418 is located 28696 bytes inside of 32768-byte region [0x62d0005f0400,0x62d0005f8400) freed by thread T148 here: #0 0x7f49627b6460 in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:52 #1 0x5593da5ac057 in cpu_exec_unrealizefn ../cpu.c:180 #2 0x5593da81f851 (/home/cota/src/qemu/build/qemu-x86_64+0x484851) Signed-off-by: Emilio Cota Reviewed-by: Richard Henderson Message-Id: <20230111151628.320011-2-cota@braap.org> Signed-off-by: Alex Bennée Message-Id: <20230124180127.1881110-27-alex.bennee@linaro.org> --- accel/tcg/cpu-exec.c | 3 +-- accel/tcg/tb-jmp-cache.h | 1 + 2 files changed, 2 insertions(+), 2 deletions(-) (limited to 'accel/tcg') diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index 04cd1f3092..25ec73ef9a 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -1064,13 +1064,12 @@ void tcg_exec_realizefn(CPUState *cpu, Error **errp) /* undo the initializations in reverse order */ void tcg_exec_unrealizefn(CPUState *cpu) { - qemu_plugin_vcpu_exit_hook(cpu); #ifndef CONFIG_USER_ONLY tcg_iommu_free_notifier_list(cpu); #endif /* !CONFIG_USER_ONLY */ tlb_destroy(cpu); - g_free(cpu->tb_jmp_cache); + g_free_rcu(cpu->tb_jmp_cache, rcu); } #ifndef CONFIG_USER_ONLY diff --git a/accel/tcg/tb-jmp-cache.h b/accel/tcg/tb-jmp-cache.h index ff5ffc8fc2..b3f6e78835 100644 --- a/accel/tcg/tb-jmp-cache.h +++ b/accel/tcg/tb-jmp-cache.h @@ -18,6 +18,7 @@ * a load_acquire/store_release to 'tb'. */ struct CPUJumpCache { + struct rcu_head rcu; struct { TranslationBlock *tb; #if TARGET_TB_PCREL -- cgit v1.2.3