diff options
| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2026-08-05 21:56:46 -0700 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2026-08-08 22:22:41 -0400 |
| commit | 8b8292d6487c81bd57c2605a9b404b1cf8f1edfb (patch) | |
| tree | ea1f2bd304c9470948aaf054b60e076fb5f548f4 /kernel/trace | |
| parent | f27bdc43077e4fcb5557dfc315ee8d91e741f483 (diff) | |
ftrace: Fix off-by-one fentry site disable in ftrace_free_mem()
When a module's init text is freed, do_init_module() calls
ftrace_free_mem() with a half-open [start, end) range. However the
ftrace_cmp_recs() comparator treats the upper bound as inclusive, as all
its other users do, passing 'ip + size - 1'. So ftrace_free_mem() can
delete a record sitting exactly at 'end', which is outside the freed
range.
For a kernel without CFI or IBT, the first record of a function is at
the function start, which for the first function in a module is also the
base of its text allocation. As the module allocator packs its regions,
that address is often the 'end' passed by a neighboring module's
do_init_module(), causing the first function's ftrace location to get
disabled, preventing an attempt to livepatch it:
livepatch: failed to find location for function 'pcspkr_probe'
Convert the exclusive end to the inclusive 'end - 1' the comparator
expects, and return early for an empty range to avoid the subtraction
from underflowing when the init text size is zero.
Cc: stable@vger.kernel.org
Fixes: 42c269c88dc1 ("ftrace: Allow for function tracing to record init functions on boot up")
Link: https://patch.msgid.link/1b5ccfa8095bdb1277f84af1c2c2e2205aca03ae.1785992188.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/ftrace.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 414e425c2d80..7c50f8ae5a0c 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -8305,7 +8305,8 @@ static void add_to_clear_hash_list(struct list_head *clear_list, void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr) { unsigned long start = (unsigned long)(start_ptr); - unsigned long end = (unsigned long)(end_ptr); + /* end is inclusive and end_ptr is exclusive */ + unsigned long end = (unsigned long)(end_ptr) - 1; struct ftrace_page **last_pg = &ftrace_pages_start; struct ftrace_page *tmp_page = NULL; struct ftrace_page *pg; @@ -8315,6 +8316,9 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr) struct ftrace_init_func *func, *func_next; LIST_HEAD(clear_hash); + if (start_ptr >= end_ptr) + return; + key.ip = start; key.flags = end; /* overload flags, as it is unsigned long */ |