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Subject[PATCH] tracing/user_events: Fix an erroneous usage of struct_size()
Date
If struct_size() returns a value that does not fit in a 'int', the size
passed to kzalloc() is wrong.

Remove the intermediate 'size' variable and use struct_size() directly.

Fixes: 7f5a08c79df3 ("user_events: Add minimal support for trace_event into ftrace")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
I don't know if 'size' can get bigger than a int in the real world, but the
change looks safe in any cases.

On x86_64, looking at the .s files, the previous code had an extra:
movslq %r13d, %r13
which really looks wrong to me.
---
kernel/trace/trace_events_user.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 33cb6af31f39..67cc71a872b0 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -2153,7 +2153,7 @@ static int user_events_ref_add(struct user_event_file_info *info,
{
struct user_event_group *group = info->group;
struct user_event_refs *refs, *new_refs;
- int i, size, count = 0;
+ int i, count = 0;

refs = rcu_dereference_protected(info->refs,
lockdep_is_held(&group->reg_mutex));
@@ -2166,10 +2166,8 @@ static int user_events_ref_add(struct user_event_file_info *info,
return i;
}

- size = struct_size(refs, events, count + 1);
-
- new_refs = kzalloc(size, GFP_KERNEL_ACCOUNT);
-
+ new_refs = kzalloc(struct_size(refs, events, count + 1),
+ GFP_KERNEL_ACCOUNT);
if (!new_refs)
return -ENOMEM;

--
2.34.1
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