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tracing/fprobe: Unregister fprobe even if memory allocation fails 

unregister_fprobe() can fail under memory pressure because of memory
allocation failure, but this maybe called from module unloading, and
usually there is no way to retry it. Moreover. trace_fprobe does not
check the return value.

To fix this problem, unregister fprobe and fprobe_hash_node even if
working memory allocation fails.
Anyway, if the last fprobe is removed, the filter will be freed.

Link: https://lore.kernel.org/all/177669365629.132053.8433032896213721288.stgit@mhiramat.tok.corp.google.com/

Fixes: 4346ba1604 ("fprobe: Rewrite fprobe on function-graph tracer")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
master
Masami Hiramatsu (Google) 2026-04-20 23:00:56 +09:00
parent 6ad51ada17
commit 1aec9e5c3e
1 changed files with 15 additions and 10 deletions
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25
kernel/trace/fprobe.c
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@ -324,9 +324,10 @@ static void fprobe_ftrace_remove_ips(unsigned long *addrs, int num)
lockdep_assert_held(&fprobe_mutex);
fprobe_ftrace_active--;
if (!fprobe_ftrace_active)
if (!fprobe_ftrace_active) {
unregister_ftrace_function(&fprobe_ftrace_ops);
if (num)
ftrace_free_filter(&fprobe_ftrace_ops);
} else if (num)
ftrace_set_filter_ips(&fprobe_ftrace_ops, addrs, num, 1, 0);
}
@ -525,10 +526,10 @@ static void fprobe_graph_remove_ips(unsigned long *addrs, int num)
fprobe_graph_active--;
/* Q: should we unregister it ? */
if (!fprobe_graph_active)
if (!fprobe_graph_active) {
unregister_ftrace_graph(&fprobe_graph_ops);
if (num)
ftrace_free_filter(&fprobe_graph_ops.ops);
} else if (num)
ftrace_set_filter_ips(&fprobe_graph_ops.ops, addrs, num, 1, 0);
}
@ -932,15 +933,19 @@ int unregister_fprobe(struct fprobe *fp)
hlist_array = fp->hlist_array;
addrs = kcalloc(hlist_array->size, sizeof(unsigned long), GFP_KERNEL);
if (!addrs) {
ret = -ENOMEM; /* TODO: Fallback to one-by-one loop */
goto out;
}
/*
* This will remove fprobe_hash_node from the hash table even if
* memory allocation fails. However, ftrace_ops will not be updated.
* Anyway, when the last fprobe is unregistered, ftrace_ops is also
* unregistered.
*/
if (!addrs)
pr_warn("Failed to allocate working array. ftrace_ops may not sync.\n");
/* Remove non-synonim ips from table and hash */
count = 0;
for (i = 0; i < hlist_array->size; i++) {
if (!delete_fprobe_node(&hlist_array->array[i]))
if (!delete_fprobe_node(&hlist_array->array[i]) && addrs)
addrs[count++] = hlist_array->array[i].addr;
}
del_fprobe_hash(fp);