From 803bdfe43083475c7df3db38dc96f4e20d05457d Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Mon, 10 Apr 2017 14:39:41 +0100 Subject: Don't delete thread_info if refcount isn't zero I build GDB with asan, and run test case hook-stop.exp, and threadapply.exp, I got the following asan error, =================================================================^M ^[[1m^[[31m==2291==ERROR: AddressSanitizer: heap-use-after-free on address 0x6160000999c4 at pc 0x000000826022 bp 0x7ffd28a8ff70 sp 0x7ffd28a8ff60^M ^[[1m^[[0m^[[1m^[[34mREAD of size 4 at 0x6160000999c4 thread T0^[[1m^[[0m^M #0 0x826021 in release_stop_context_cleanup ../../binutils-gdb/gdb/infrun.c:8203^M #1 0x72798a in do_my_cleanups ../../binutils-gdb/gdb/common/cleanups.c:154^M #2 0x727a32 in do_cleanups(cleanup*) ../../binutils-gdb/gdb/common/cleanups.c:176^M #3 0x826895 in normal_stop() ../../binutils-gdb/gdb/infrun.c:8381^M #4 0x815208 in fetch_inferior_event(void*) ../../binutils-gdb/gdb/infrun.c:4011^M #5 0x868aca in inferior_event_handler(inferior_event_type, void*) ../../binutils-gdb/gdb/inf-loop.c:44^M .... ^[[1m^[[32m0x6160000999c4 is located 68 bytes inside of 568-byte region [0x616000099980,0x616000099bb8)^M ^[[1m^[[0m^[[1m^[[35mfreed by thread T0 here:^[[1m^[[0m^M #0 0x7fb0bc1312ca in __interceptor_free (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x982ca)^M #1 0xb8c62f in xfree(void*) ../../binutils-gdb/gdb/common/common-utils.c:100^M #2 0x83df67 in free_thread ../../binutils-gdb/gdb/thread.c:207^M #3 0x83dfd2 in init_thread_list() ../../binutils-gdb/gdb/thread.c:223^M #4 0x805494 in kill_command ../../binutils-gdb/gdb/infcmd.c:2595^M .... Detaching from program: /home/yao.qi/SourceCode/gnu/build-with-asan/gdb/testsuite/outputs/gdb.threads/threadapply/threadapply, process 2399^M =================================================================^M ^[[1m^[[31m==2387==ERROR: AddressSanitizer: heap-use-after-free on address 0x6160000a98c0 at pc 0x00000083fd28 bp 0x7ffd401c3110 sp 0x7ffd401c3100^M ^[[1m^[[0m^[[1m^[[34mREAD of size 4 at 0x6160000a98c0 thread T0^[[1m^[[0m^M #0 0x83fd27 in thread_alive ../../binutils-gdb/gdb/thread.c:741^M #1 0x844277 in thread_apply_all_command ../../binutils-gdb/gdb/thread.c:1804^M .... ^M ^[[1m^[[32m0x6160000a98c0 is located 64 bytes inside of 568-byte region [0x6160000a9880,0x6160000a9ab8)^M ^[[1m^[[0m^[[1m^[[35mfreed by thread T0 here:^[[1m^[[0m^M #0 0x7f59a7e322ca in __interceptor_free (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x982ca)^M #1 0xb8c62f in xfree(void*) ../../binutils-gdb/gdb/common/common-utils.c:100^M #2 0x83df67 in free_thread ../../binutils-gdb/gdb/thread.c:207^M #3 0x83dfd2 in init_thread_list() ../../binutils-gdb/gdb/thread.c:223^M This patch fixes the issue by deleting thread_info object if it is deletable, otherwise, mark it as exited (by set_thread_exited). Function set_thread_exited is shared from delete_thread_1. This patch also moves field "refcount" to private and methods incref and decref. Additionally, we stop using "ptid_t" in "struct current_thread_cleanup" to reference threads, instead we use "thread_info" directly. Due to this change, we don't need restore_current_thread_ptid_changed anymore. gdb: 2017-04-10 Yao Qi PR gdb/19942 * gdbthread.h (thread_info::deletable): New method. (thread_info::incref): New method. (thread_info::decref): New method. (thread_info::refcount): Move it to private. * infrun.c (save_stop_context): Call inc_refcount. (release_stop_context_cleanup): Likewise. * thread.c (set_thread_exited): New function. (init_thread_list): Delete "tp" only it is deletable, otherwise call set_thread_exited. (delete_thread_1): Call set_thread_exited. (current_thread_cleanup) : Remove. : New field. (restore_current_thread_ptid_changed): Removed. (do_restore_current_thread_cleanup): Adjust. (restore_current_thread_cleanup_dtor): Don't call find_thread_ptid. (set_thread_refcount): Use dec_refcount. (make_cleanup_restore_current_thread): Adjust. (thread_apply_all_command): Call inc_refcount. (_initialize_thread): Don't call observer_attach_thread_ptid_changed. --- gdb/gdbthread.h | 33 ++++++++++++++++++++++++++++----- 1 file changed, 28 insertions(+), 5 deletions(-) (limited to 'gdb/gdbthread.h') diff --git a/gdb/gdbthread.h b/gdb/gdbthread.h index 9a16fe6..4cd7390 100644 --- a/gdb/gdbthread.h +++ b/gdb/gdbthread.h @@ -183,6 +183,27 @@ public: explicit thread_info (inferior *inf, ptid_t ptid); ~thread_info (); + bool deletable () const + { + /* If this is the current thread, or there's code out there that + relies on it existing (m_refcount > 0) we can't delete yet. */ + return (m_refcount == 0 && !ptid_equal (ptid, inferior_ptid)); + } + + /* Increase the refcount. */ + void incref () + { + gdb_assert (m_refcount >= 0); + m_refcount++; + } + + /* Decrease the refcount. */ + void decref () + { + m_refcount--; + gdb_assert (m_refcount >= 0); + } + struct thread_info *next = NULL; ptid_t ptid; /* "Actual process id"; In fact, this may be overloaded with @@ -254,11 +275,6 @@ public: but STATE will still be THREAD_RUNNING. */ enum thread_state state = THREAD_STOPPED; - /* If this is > 0, then it means there's code out there that relies - on this thread being listed. Don't delete it from the lists even - if we detect it exiting. */ - int refcount = 0; - /* State of GDB control of inferior thread execution. See `struct thread_control_state'. */ thread_control_state control {}; @@ -346,6 +362,13 @@ public: fields point to self. */ struct thread_info *step_over_prev = NULL; struct thread_info *step_over_next = NULL; + +private: + + /* If this is > 0, then it means there's code out there that relies + on this thread being listed. Don't delete it from the lists even + if we detect it exiting. */ + int m_refcount = 0; }; /* Create an empty thread list, or empty the existing one. */ -- cgit v1.1