5.4-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt rostedt@goodmis.org
commit bfb336cf97df7b37b2b2edec0f69773e06d11955 upstream.
Currently the reader of set_ftrace_filter and set_ftrace_notrace just adds the pointer to the global tracer hash to its iterator. Unlike the writer that allocates a copy of the hash, the reader keeps the pointer to the filter hashes. This is problematic because this pointer is static across function calls that release the locks that can update the global tracer hashes. This can cause UAF and similar bugs.
Allocate and copy the hash for reading the filter files like it is done for the writers. This not only fixes UAF bugs, but also makes the code a bit simpler as it doesn't have to differentiate when to free the iterator's hash between writers and readers.
Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Nathan Chancellor nathan@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Link: https://lore.kernel.org/20250822183606.12962cc3@batman.local.home Fixes: c20489dad156 ("ftrace: Assign iter->hash to filter or notrace hashes on seq read") Closes: https://lore.kernel.org/all/20250813023044.2121943-1-wutengda@huaweicloud.co... Closes: https://lore.kernel.org/all/20250822192437.GA458494@ax162/ Reported-by: Tengda Wu wutengda@huaweicloud.com Tested-by: Tengda Wu wutengda@huaweicloud.com Tested-by: Nathan Chancellor nathan@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/ftrace.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)
--- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -3650,13 +3650,17 @@ ftrace_regex_open(struct ftrace_ops *ops } else { iter->hash = alloc_and_copy_ftrace_hash(size_bits, hash); } + } else { + if (hash) + iter->hash = alloc_and_copy_ftrace_hash(hash->size_bits, hash); + else + iter->hash = EMPTY_HASH; + }
- if (!iter->hash) { - trace_parser_put(&iter->parser); - goto out_unlock; - } - } else - iter->hash = hash; + if (!iter->hash) { + trace_parser_put(&iter->parser); + goto out_unlock; + }
ret = 0;
@@ -5117,9 +5121,6 @@ int ftrace_regex_release(struct inode *i ret = ftrace_hash_move_and_update_ops(iter->ops, orig_hash, iter->hash, filter_hash); mutex_unlock(&ftrace_lock); - } else { - /* For read only, the hash is the ops hash */ - iter->hash = NULL; }
mutex_unlock(&iter->ops->func_hash->regex_lock);