On Wed, 13 Aug 2025 02:30:43 +0000
Tengda Wu <[email protected]> wrote:
> The free_ftrace_hash call is just unnecessary in this context since
> we shouldn't free the global hash that we don't own. Remove this call
> to fix the issue.
This is incorrect as it is only unnecessary if it's a read.
The code above is:
if (file->f_mode & FMODE_WRITE) {
const int size_bits = FTRACE_HASH_DEFAULT_BITS;
if (file->f_flags & O_TRUNC) {
iter->hash = alloc_ftrace_hash(size_bits);
clear_ftrace_mod_list(mod_head);
} else {
iter->hash = alloc_and_copy_ftrace_hash(size_bits,
hash);
}
if (!iter->hash) {
trace_parser_put(&iter->parser);
goto out_unlock;
}
} else
iter->hash = hash;
Where if the file was open for write, the hash must be freed.
>
> Fixes: c20489dad156 ("ftrace: Assign iter->hash to filter or notrace hashes
> on seq read")
> Signed-off-by: Tengda Wu <[email protected]>
> ---
> kernel/trace/ftrace.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 00b76d450a89..cade13595b08 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -4680,7 +4680,6 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
> m->private = iter;
> } else {
> /* Failed */
> - free_ftrace_hash(iter->hash);
The real fix is:
if (file->f_mode & FMODE_WRITE)
free_ftrace_hash(iter->hash);
-- Steve
> trace_parser_put(&iter->parser);
> }
> } else
