6.14-stable review patch. If anyone has any objections, please let me know.
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From: Masami Hiramatsu (Google) mhiramat@kernel.org
commit dd941507a9486252d6fcf11814387666792020f3 upstream.
Commit ac91052f0ae5 ("tracing: tprobe-events: Fix leakage of module refcount") moved try_module_get() from __find_tracepoint_module_cb() to find_tracepoint() caller, but that introduced a possible UAF because the module can be unloaded before try_module_get(). In this case, the module object should be freed too. Thus, try_module_get() does not only fail but may access to the freed object.
To avoid that, try_module_get() in __find_tracepoint_module_cb() again.
Link: https://lore.kernel.org/all/174342990779.781946.9138388479067729366.stgit@de...
Fixes: ac91052f0ae5 ("tracing: tprobe-events: Fix leakage of module refcount") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu (Google) mhiramat@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/trace_fprobe.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-)
--- a/kernel/trace/trace_fprobe.c +++ b/kernel/trace/trace_fprobe.c @@ -919,9 +919,15 @@ static void __find_tracepoint_module_cb( struct __find_tracepoint_cb_data *data = priv;
if (!data->tpoint && !strcmp(data->tp_name, tp->name)) { - data->tpoint = tp; - if (!data->mod) + /* If module is not specified, try getting module refcount. */ + if (!data->mod && mod) { + /* If failed to get refcount, ignore this tracepoint. */ + if (!try_module_get(mod)) + return; + data->mod = mod; + } + data->tpoint = tp; } }
@@ -933,7 +939,11 @@ static void __find_tracepoint_cb(struct data->tpoint = tp; }
-/* Find a tracepoint from kernel and module. */ +/* + * Find a tracepoint from kernel and module. If the tracepoint is on the module, + * the module's refcount is incremented and returned as *@tp_mod. Thus, if it is + * not NULL, caller must call module_put(*tp_mod) after used the tracepoint. + */ static struct tracepoint *find_tracepoint(const char *tp_name, struct module **tp_mod) { @@ -962,7 +972,10 @@ static void reenable_trace_fprobe(struct } }
-/* Find a tracepoint from specified module. */ +/* + * Find a tracepoint from specified module. In this case, this does not get the + * module's refcount. The caller must ensure the module is not freed. + */ static struct tracepoint *find_tracepoint_in_module(struct module *mod, const char *tp_name) { @@ -1169,11 +1182,6 @@ static int trace_fprobe_create_internal( if (is_tracepoint) { ctx->flags |= TPARG_FL_TPOINT; tpoint = find_tracepoint(symbol, &tp_mod); - /* lock module until register this tprobe. */ - if (tp_mod && !try_module_get(tp_mod)) { - tpoint = NULL; - tp_mod = NULL; - } if (tpoint) { ctx->funcname = kallsyms_lookup( (unsigned long)tpoint->probestub,