From b315b67d7a57a0fd995cce5dfec77a4b61fa23d4 Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Mon, 13 Jul 2020 22:27:00 -0400 Subject: [PATCH] gdbserver: fix memory leak when handling qsupported packet When building gdbserver with AddressSanitizer, I get this annoying little leak when gdbserver exits: ==307817==ERROR: LeakSanitizer: detected memory leaks Direct leak of 14 byte(s) in 1 object(s) allocated from: #0 0x7f7fd4256459 in __interceptor_malloc /build/gcc/src/gcc/libsanitizer/asan/asan_malloc_linux.cpp:145 #1 0x563bef981b80 in xmalloc /home/simark/src/binutils-gdb/gdbserver/../gdb/alloc.c:60 #2 0x563befb53301 in xstrdup /home/simark/src/binutils-gdb/libiberty/xstrdup.c:34 #3 0x563bef9d742b in handle_query /home/simark/src/binutils-gdb/gdbserver/server.cc:2286 #4 0x563bef9ed0b7 in process_serial_event /home/simark/src/binutils-gdb/gdbserver/server.cc:4061 #5 0x563bef9f1d9e in handle_serial_event(int, void*) /home/simark/src/binutils-gdb/gdbserver/server.cc:4402 #6 0x563befb0ec65 in handle_file_event /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:548 #7 0x563befb0f49f in gdb_wait_for_event /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:673 #8 0x563befb0d4a1 in gdb_do_one_event() /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:215 #9 0x563bef9e721a in start_event_loop /home/simark/src/binutils-gdb/gdbserver/server.cc:3484 #10 0x563bef9eb90a in captured_main /home/simark/src/binutils-gdb/gdbserver/server.cc:3875 #11 0x563bef9ec2c7 in main /home/simark/src/binutils-gdb/gdbserver/server.cc:3961 #12 0x7f7fd3330001 in __libc_start_main (/usr/lib/libc.so.6+0x27001) SUMMARY: AddressSanitizer: 14 byte(s) leaked in 1 allocation(s). This is due to the handling of unknown qsupported features in handle_query. The `qsupported` vector is built, containing all the feature names received from GDB. As we iterate on them, when we encounter unknown ones, we move them at the beginning of the vector, in preparation of passing this vector of unknown features down to the target (which may know about them). When moving these unknown features to other slots in the vector, we overwrite other pointers without freeing them, which therefore leak. An easy fix would be to add a `free` when doing the move. However, I think this is a good opportunity to sprinkle a bit of automatic memory management in this code. So, use a vector of std::string which owns all the entries. And use a separate vector (that doesn't own the entries) for the unknown ones, which is then passed to target_process_qsupported. Given that the `c_str` method of std::string returns a `const char *`, it follows that process_stratum_target::process_qsupported must accept a `const char **` instead of a `char **`. And while at it, change the pointer + size paramters to use an array_view instead. gdbserver/ChangeLog: * server.cc (handle_query): Use std::vector of std::string for `qsupported` vector. Use separate vector for unknowns. * target.h (class process_stratum_target) : Change parameters to array_view of const char *. (target_process_qsupported): Remove `count` parameter. * target.cc (process_stratum_target::process_qsupported): Change parameters to array_view of const char *. * linux-x86-low.cc (class x86_target) : Likewise. Change-Id: I97f133825faa6d7abbf83a58504eb0ba77462812 --- gdbserver/ChangeLog | 13 +++++++++++ gdbserver/linux-x86-low.cc | 12 +++++----- gdbserver/server.cc | 45 ++++++++++++++------------------------ gdbserver/target.cc | 3 ++- gdbserver/target.h | 10 +++++---- 5 files changed, 42 insertions(+), 41 deletions(-) diff --git a/gdbserver/ChangeLog b/gdbserver/ChangeLog index 4ed5d610161..1ee716f52d7 100644 --- a/gdbserver/ChangeLog +++ b/gdbserver/ChangeLog @@ -1,3 +1,16 @@ +2020-07-13 Simon Marchi + + * server.cc (handle_query): Use std::vector of + std::string for `qsupported` vector. Use separate + vector for unknowns. + * target.h (class process_stratum_target) : + Change parameters to array_view of const char *. + (target_process_qsupported): Remove `count` parameter. + * target.cc (process_stratum_target::process_qsupported): Change + parameters to array_view of const char *. + * linux-x86-low.cc (class x86_target) : + Likewise. + 2020-06-29 Tom de Vries * ax.h: Include gdbsupport/debug_agent.h. diff --git a/gdbserver/linux-x86-low.cc b/gdbserver/linux-x86-low.cc index 7a65c1d079f..37d3626e1f7 100644 --- a/gdbserver/linux-x86-low.cc +++ b/gdbserver/linux-x86-low.cc @@ -106,7 +106,7 @@ class x86_target : public linux_process_target bool supports_z_point_type (char z_type) override; - void process_qsupported (char **features, int count) override; + void process_qsupported (gdb::array_view features) override; bool supports_tracepoints () override; @@ -1003,18 +1003,15 @@ x86_target::update_xmltarget () PTRACE_GETREGSET. */ void -x86_target::process_qsupported (char **features, int count) +x86_target::process_qsupported (gdb::array_view features) { - int i; - /* Return if gdb doesn't support XML. If gdb sends "xmlRegisters=" with "i386" in qSupported query, it supports x86 XML target descriptions. */ use_xml = 0; - for (i = 0; i < count; i++) - { - const char *feature = features[i]; + for (const char *feature : features) + { if (startswith (feature, "xmlRegisters=")) { char *copy = xstrdup (feature + 13); @@ -1034,6 +1031,7 @@ x86_target::process_qsupported (char **features, int count) free (copy); } } + update_xmltarget (); } diff --git a/gdbserver/server.cc b/gdbserver/server.cc index 0313d18bb24..ab5363eb032 100644 --- a/gdbserver/server.cc +++ b/gdbserver/server.cc @@ -2269,10 +2269,8 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p) ';'. */ if (*p == ':') { - char **qsupported = NULL; - int count = 0; - int unknown = 0; - int i; + std::vector qsupported; + std::vector unknowns; /* Two passes, to avoid nested strtok calls in target_process_qsupported. */ @@ -2280,28 +2278,23 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p) for (p = strtok_r (p + 1, ";", &saveptr); p != NULL; p = strtok_r (NULL, ";", &saveptr)) - { - count++; - qsupported = XRESIZEVEC (char *, qsupported, count); - qsupported[count - 1] = xstrdup (p); - } + qsupported.emplace_back (p); - for (i = 0; i < count; i++) + for (const std::string &feature : qsupported) { - p = qsupported[i]; - if (strcmp (p, "multiprocess+") == 0) + if (feature == "multiprocess+") { /* GDB supports and wants multi-process support if possible. */ if (target_supports_multi_process ()) cs.multi_process = 1; } - else if (strcmp (p, "qRelocInsn+") == 0) + else if (feature == "qRelocInsn+") { /* GDB supports relocate instruction requests. */ gdb_supports_qRelocInsn = 1; } - else if (strcmp (p, "swbreak+") == 0) + else if (feature == "swbreak+") { /* GDB wants us to report whether a trap is caused by a software breakpoint and for us to handle PC @@ -2309,36 +2302,36 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p) if (target_supports_stopped_by_sw_breakpoint ()) cs.swbreak_feature = 1; } - else if (strcmp (p, "hwbreak+") == 0) + else if (feature == "hwbreak+") { /* GDB wants us to report whether a trap is caused by a hardware breakpoint. */ if (target_supports_stopped_by_hw_breakpoint ()) cs.hwbreak_feature = 1; } - else if (strcmp (p, "fork-events+") == 0) + else if (feature == "fork-events+") { /* GDB supports and wants fork events if possible. */ if (target_supports_fork_events ()) cs.report_fork_events = 1; } - else if (strcmp (p, "vfork-events+") == 0) + else if (feature == "vfork-events+") { /* GDB supports and wants vfork events if possible. */ if (target_supports_vfork_events ()) cs.report_vfork_events = 1; } - else if (strcmp (p, "exec-events+") == 0) + else if (feature == "exec-events+") { /* GDB supports and wants exec events if possible. */ if (target_supports_exec_events ()) cs.report_exec_events = 1; } - else if (strcmp (p, "vContSupported+") == 0) + else if (feature == "vContSupported+") cs.vCont_supported = 1; - else if (strcmp (p, "QThreadEvents+") == 0) + else if (feature == "QThreadEvents+") ; - else if (strcmp (p, "no-resumed+") == 0) + else if (feature == "no-resumed+") { /* GDB supports and wants TARGET_WAITKIND_NO_RESUMED events. */ @@ -2347,19 +2340,13 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p) else { /* Move the unknown features all together. */ - qsupported[i] = NULL; - qsupported[unknown] = p; - unknown++; + unknowns.push_back (feature.c_str ()); } } /* Give the target backend a chance to process the unknown features. */ - target_process_qsupported (qsupported, unknown); - - for (i = 0; i < count; i++) - free (qsupported[i]); - free (qsupported); + target_process_qsupported (unknowns); } sprintf (own_buf, diff --git a/gdbserver/target.cc b/gdbserver/target.cc index b5190e1f52a..87f62a0b555 100644 --- a/gdbserver/target.cc +++ b/gdbserver/target.cc @@ -599,7 +599,8 @@ process_stratum_target::read_loadmap (const char *annex, } void -process_stratum_target::process_qsupported (char **features, int count) +process_stratum_target::process_qsupported + (gdb::array_view features) { /* Nop. */ } diff --git a/gdbserver/target.h b/gdbserver/target.h index 701c8ef8767..13f069f7729 100644 --- a/gdbserver/target.h +++ b/gdbserver/target.h @@ -27,6 +27,7 @@ #include "target/wait.h" #include "target/waitstatus.h" #include "mem-break.h" +#include "gdbsupport/array-view.h" #include "gdbsupport/btrace-common.h" #include @@ -315,8 +316,9 @@ class process_stratum_target unsigned char *myaddr, unsigned int len); /* Target specific qSupported support. FEATURES is an array of - features with COUNT elements. */ - virtual void process_qsupported (char **features, int count); + features unsupported by the core of GDBserver. */ + virtual void process_qsupported + (gdb::array_view features); /* Return true if the target supports tracepoints, false otherwise. */ virtual bool supports_tracepoints (); @@ -547,8 +549,8 @@ int kill_inferior (process_info *proc); #define target_async(enable) \ the_target->async (enable) -#define target_process_qsupported(features, count) \ - the_target->process_qsupported (features, count) +#define target_process_qsupported(features) \ + the_target->process_qsupported (features) #define target_supports_catch_syscall() \ the_target->supports_catch_syscall ()