From: Steven Rostedt <rostedt@goodmis.org> mainline inclusion from mainline-v7.3-rc2 commit f2951ebd15c36a1ea4820a7f0cbb0b5f1c028b73 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/19114 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- The options files do not take the trace_array reference for the options they represent. This could cause a use-after-free kernel crash if one of these files is opened by one task and another task removes the instance that the option is for. Because it doesn't take a reference upon opening, it will not stop the removal which will free the options descriptor that is being used. As the options are somewhat dynamic in their creation at boot up, each file represents a flag in the trace_array. The trace_array has an array of indexes to represent each of these flags that is stored in the trace_flags_index array. The address of the index array element is used to pass to the inode->i_private pointer. Then that element is read which holds the index (which represents the flag) and then the index is used to calculate the trace_array descriptor from its trace_flags_index array. One issue is that the index element can not be referenced until the trace_array's reference is taken. To handle this, create a new helper function called: trace_array_options_get() that will iterate all the existing trace_arrays in the ftrace_trace_arrays list (under the trace_types_lock), and compare the passed in address of the index element with the entire array of the trace_array's trace_flags_index array. If it matches, then up the corresponding trace_array's reference and return. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902121918.5a9e9d1b@gandalf.local.home Fixes: 577b785f55168 ("tracing: add tracer dependent options to options directory") Reported-by: sashiko-bot@kernel.org Closes: https://lore.kernel.org/linux-trace-kernel/20260828135858.2AC501F000E9@smtp.... Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Conflicts: kernel/trace/trace.c [This version lacks the lock-free __trace_array_get, which is hidden inside a refactoring patch in the mainline, commit eca33fdab47b. To avoid introducing that refactoring patch, __trace_array_get was manually adapted.] Signed-off-by: Tengda Wu <wutengda2@huawei.com> --- kernel/trace/trace.c | 79 ++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 73 insertions(+), 6 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8c4e4cfa2945..7a57721c1a54 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -433,6 +433,12 @@ static struct trace_array global_trace = { LIST_HEAD(ftrace_trace_arrays); +static int __trace_array_get(struct trace_array *this_tr) +{ + this_tr->ref++; + return 0; +} + int trace_array_get(struct trace_array *this_tr) { struct trace_array *tr; @@ -441,8 +447,7 @@ int trace_array_get(struct trace_array *this_tr) mutex_lock(&trace_types_lock); list_for_each_entry(tr, &ftrace_trace_arrays, list) { if (tr == this_tr) { - tr->ref++; - ret = 0; + ret = __trace_array_get(tr); break; } } @@ -8538,11 +8543,73 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt, return cnt; } +/* + * The tr_index is the address of a trace_array->trace_flags_index[] + * element that holds the index of the trace flag. But since the + * trace_array reference has not been taken yet, it cannot be referenced + * as it could have been freed by a rmdir of the instance the trace_array + * represents. + * + * Search the list of trace_arrays and compare the tr_index to the + * address of the entire trace_array trace_flags_index array for each + * trace_array in the list. If one is matched, then take the reference + * and return it. If not, the trace_array no longer exits. + */ +static int trace_array_options_get(void *tr_index) +{ + struct trace_array *tr; + int ret; + + ret = security_locked_down(LOCKDOWN_TRACEFS); + if (ret) + return ret; + + if (tracing_disabled) + return -ENODEV; + + mutex_lock(&trace_types_lock); + list_for_each_entry(tr, &ftrace_trace_arrays, list) { + if (tr_index >= (void *)&tr->trace_flags_index[0] && + tr_index < (void *)&tr->trace_flags_index[TRACE_FLAGS_MAX_SIZE]) { + mutex_unlock(&trace_types_lock); + return __trace_array_get(tr); + } + } + mutex_unlock(&trace_types_lock); + return -ENODEV; +} + +static int trace_options_open(struct inode *inode, struct file *filp) +{ + void *tr_index = inode->i_private; + + if (trace_array_options_get(tr_index) < 0) + return -ENODEV; + + filp->private_data = tr_index; + + return 0; +} + +static int trace_options_release(struct inode *inode, struct file *filp) +{ + void *tr_index = filp->private_data; + struct trace_array *tr; + unsigned int index; + + get_tr_index(tr_index, &tr, &index); + + trace_array_put(tr); + + return 0; +} + static const struct file_operations trace_options_core_fops = { - .open = tracing_open_generic, - .read = trace_options_core_read, - .write = trace_options_core_write, - .llseek = generic_file_llseek, + .open = trace_options_open, + .read = trace_options_core_read, + .write = trace_options_core_write, + .llseek = generic_file_llseek, + .release = trace_options_release, }; struct dentry *trace_create_file(const char *name, -- 2.34.1