| Message ID | 20230816054357.1188339-1-zhengyejian1@huawei.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] tracing: Fix memleak due to race between current_tracer and trace | expand |
On Wed, 16 Aug 2023 13:43:57 +0800 Zheng Yejian <zhengyejian1@huawei.com> wrote: > Kmemleak report a leak in graph_trace_open(): > > unreferenced object 0xffff0040b95f4a00 (size 128): > comm "cat", pid 204981, jiffies 4301155872 (age 99771.964s) > hex dump (first 32 bytes): > e0 05 e7 b4 ab 7d 00 00 0b 00 01 00 00 00 00 00 .....}.......... > f4 00 01 10 00 a0 ff ff 00 00 00 00 65 00 10 00 ............e... > backtrace: > [<000000005db27c8b>] kmem_cache_alloc_trace+0x348/0x5f0 > [<000000007df90faa>] graph_trace_open+0xb0/0x344 > [<00000000737524cd>] __tracing_open+0x450/0xb10 > [<0000000098043327>] tracing_open+0x1a0/0x2a0 > [<00000000291c3876>] do_dentry_open+0x3c0/0xdc0 > [<000000004015bcd6>] vfs_open+0x98/0xd0 > [<000000002b5f60c9>] do_open+0x520/0x8d0 > [<00000000376c7820>] path_openat+0x1c0/0x3e0 > [<00000000336a54b5>] do_filp_open+0x14c/0x324 > [<000000002802df13>] do_sys_openat2+0x2c4/0x530 > [<0000000094eea458>] __arm64_sys_openat+0x130/0x1c4 > [<00000000a71d7881>] el0_svc_common.constprop.0+0xfc/0x394 > [<00000000313647bf>] do_el0_svc+0xac/0xec > [<000000002ef1c651>] el0_svc+0x20/0x30 > [<000000002fd4692a>] el0_sync_handler+0xb0/0xb4 > [<000000000c309c35>] el0_sync+0x160/0x180 > > The root cause is descripted as follows: > > __tracing_open() { // 1. File 'trace' is being opened; > ... > *iter->trace = *tr->current_trace; // 2. Tracer 'function_graph' is > // currently set; > ... > iter->trace->open(iter); // 3. Call graph_trace_open() here, > // and memory are allocated in it; > ... > } > > s_start() { // 4. The opened file is being read; > ... > *iter->trace = *tr->current_trace; // 5. If tracer is switched to > // 'nop' or others, then memory > // in step 3 are leaked!!! > ... > } > > To fix it, in s_start(), close tracer before switching then reopen the > new tracer after switching. And some tracers like 'wakeup' may not update > 'iter->private' in some cases when reopen, so clear 'iter->private' in > graph_trace_close() to avoid it being mistakenly closed again. > > Fixes: d7350c3f4569 ("tracing/core: make the read callbacks reentrants") > Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> > --- > > v2: > - Fix an use-after-free issue which is due to some tracers like 'wakeup' > may not update 'iter->private' in some cases when reopen, so clear > 'iter->private' in graph_trace_close() to avoid it being mistakenly > closed again. Also update the commit message. > Link: https://lore.kernel.org/all/8c853c0c-84f0-c8be-3020-561db6f87081@huawei.com/ > > v1: > - Link: https://lore.kernel.org/all/20230808092905.2936459-1-zhengyejian1@huawei.com/ > > kernel/trace/trace.c | 9 ++++++++- > kernel/trace/trace_functions_graph.c | 1 + > 2 files changed, 9 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index b8870078ef58..d50a0227baa3 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -4213,8 +4213,15 @@ static void *s_start(struct seq_file *m, loff_t *pos) > * will point to the same string as current_trace->name. > */ > mutex_lock(&trace_types_lock); > - if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) > + if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) { > + /* Close iter->trace before switching to the new current tracer */ > + if (iter->trace->close) > + iter->trace->close(iter); > *iter->trace = *tr->current_trace; > + /* Reopen the new current tracer */ > + if (iter->trace->open) > + iter->trace->open(iter); > + } > mutex_unlock(&trace_types_lock); > > #ifdef CONFIG_TRACER_MAX_TRACE > diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c > index c35fbaab2a47..4d4808186a0f 100644 > --- a/kernel/trace/trace_functions_graph.c > +++ b/kernel/trace/trace_functions_graph.c > @@ -1317,6 +1317,7 @@ void graph_trace_close(struct trace_iterator *iter) > if (data) { > free_percpu(data->cpu_data); > kfree(data); > + iter->private = NULL; This is the wrong place to clear private. It shouldn't be up to function_graph tracer to know to clear it so that it doesn't break other tracers. If the wakeup function requires iter->private to be NULL, then it should clear it on open. -- Steve > } > } >
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index b8870078ef58..d50a0227baa3 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4213,8 +4213,15 @@ static void *s_start(struct seq_file *m, loff_t *pos) * will point to the same string as current_trace->name. */ mutex_lock(&trace_types_lock); - if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) + if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) { + /* Close iter->trace before switching to the new current tracer */ + if (iter->trace->close) + iter->trace->close(iter); *iter->trace = *tr->current_trace; + /* Reopen the new current tracer */ + if (iter->trace->open) + iter->trace->open(iter); + } mutex_unlock(&trace_types_lock); #ifdef CONFIG_TRACER_MAX_TRACE diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c index c35fbaab2a47..4d4808186a0f 100644 --- a/kernel/trace/trace_functions_graph.c +++ b/kernel/trace/trace_functions_graph.c @@ -1317,6 +1317,7 @@ void graph_trace_close(struct trace_iterator *iter) if (data) { free_percpu(data->cpu_data); kfree(data); + iter->private = NULL; } }
Kmemleak report a leak in graph_trace_open(): unreferenced object 0xffff0040b95f4a00 (size 128): comm "cat", pid 204981, jiffies 4301155872 (age 99771.964s) hex dump (first 32 bytes): e0 05 e7 b4 ab 7d 00 00 0b 00 01 00 00 00 00 00 .....}.......... f4 00 01 10 00 a0 ff ff 00 00 00 00 65 00 10 00 ............e... backtrace: [<000000005db27c8b>] kmem_cache_alloc_trace+0x348/0x5f0 [<000000007df90faa>] graph_trace_open+0xb0/0x344 [<00000000737524cd>] __tracing_open+0x450/0xb10 [<0000000098043327>] tracing_open+0x1a0/0x2a0 [<00000000291c3876>] do_dentry_open+0x3c0/0xdc0 [<000000004015bcd6>] vfs_open+0x98/0xd0 [<000000002b5f60c9>] do_open+0x520/0x8d0 [<00000000376c7820>] path_openat+0x1c0/0x3e0 [<00000000336a54b5>] do_filp_open+0x14c/0x324 [<000000002802df13>] do_sys_openat2+0x2c4/0x530 [<0000000094eea458>] __arm64_sys_openat+0x130/0x1c4 [<00000000a71d7881>] el0_svc_common.constprop.0+0xfc/0x394 [<00000000313647bf>] do_el0_svc+0xac/0xec [<000000002ef1c651>] el0_svc+0x20/0x30 [<000000002fd4692a>] el0_sync_handler+0xb0/0xb4 [<000000000c309c35>] el0_sync+0x160/0x180 The root cause is descripted as follows: __tracing_open() { // 1. File 'trace' is being opened; ... *iter->trace = *tr->current_trace; // 2. Tracer 'function_graph' is // currently set; ... iter->trace->open(iter); // 3. Call graph_trace_open() here, // and memory are allocated in it; ... } s_start() { // 4. The opened file is being read; ... *iter->trace = *tr->current_trace; // 5. If tracer is switched to // 'nop' or others, then memory // in step 3 are leaked!!! ... } To fix it, in s_start(), close tracer before switching then reopen the new tracer after switching. And some tracers like 'wakeup' may not update 'iter->private' in some cases when reopen, so clear 'iter->private' in graph_trace_close() to avoid it being mistakenly closed again. Fixes: d7350c3f4569 ("tracing/core: make the read callbacks reentrants") Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> --- v2: - Fix an use-after-free issue which is due to some tracers like 'wakeup' may not update 'iter->private' in some cases when reopen, so clear 'iter->private' in graph_trace_close() to avoid it being mistakenly closed again. Also update the commit message. Link: https://lore.kernel.org/all/8c853c0c-84f0-c8be-3020-561db6f87081@huawei.com/ v1: - Link: https://lore.kernel.org/all/20230808092905.2936459-1-zhengyejian1@huawei.com/ kernel/trace/trace.c | 9 ++++++++- kernel/trace/trace_functions_graph.c | 1 + 2 files changed, 9 insertions(+), 1 deletion(-)