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get rid of perf_fget_light(), convert kernel/events/core.c to CLASS(fd)

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Lift fdget() and fdput() out of perf_fget_light(), turning it into
is_perf_file(struct fd f).  The life gets easier in both callers
if we do fdget() unconditionally, including the case when we are
given -1 instead of a descriptor - that avoids a reassignment in
perf_event_open(2) and it avoids a nasty temptation in _perf_ioctl()
where we must *not* lift output_event out of scope for output.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2024-06-02 14:25:46 -04:00
parent 919a7a1aac
commit 4dd53b84ff
1 changed files with 16 additions and 33 deletions
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49
kernel/events/core.c
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@@ -5998,18 +5998,9 @@ EXPORT_SYMBOL_GPL(perf_event_period);
static const struct file_operations perf_fops;
static inline int perf_fget_light(int fd, struct fd *p)
static inline bool is_perf_file(struct fd f)
{
struct fd f = fdget(fd);
if (!fd_file(f))
return -EBADF;
if (fd_file(f)->f_op != &perf_fops) {
fdput(f);
return -EBADF;
}
*p = f;
return 0;
return !fd_empty(f) && fd_file(f)->f_op == &perf_fops;
}
static int perf_event_set_output(struct perf_event *event,
@@ -6057,20 +6048,14 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
case PERF_EVENT_IOC_SET_OUTPUT:
{
int ret;
CLASS(fd, output)(arg); // arg == -1 => empty
struct perf_event *output_event = NULL;
if (arg != -1) {
struct perf_event *output_event;
struct fd output;
ret = perf_fget_light(arg, &output);
if (ret)
return ret;
if (!is_perf_file(output))
return -EBADF;
output_event = fd_file(output)->private_data;
ret = perf_event_set_output(event, output_event);
fdput(output);
} else {
ret = perf_event_set_output(event, NULL);
}
return ret;
return perf_event_set_output(event, output_event);
}
case PERF_EVENT_IOC_SET_FILTER:
@@ -12664,7 +12649,6 @@ SYSCALL_DEFINE5(perf_event_open,
struct perf_event_attr attr;
struct perf_event_context *ctx;
struct file *event_file = NULL;
struct fd group = EMPTY_FD;
struct task_struct *task = NULL;
struct pmu *pmu;
int event_fd;
@@ -12735,10 +12719,12 @@ SYSCALL_DEFINE5(perf_event_open,
if (event_fd < 0)
return event_fd;
CLASS(fd, group)(group_fd); // group_fd == -1 => empty
if (group_fd != -1) {
err = perf_fget_light(group_fd, &group);
if (err)
if (!is_perf_file(group)) {
err = -EBADF;
goto err_fd;
}
group_leader = fd_file(group)->private_data;
if (flags & PERF_FLAG_FD_OUTPUT)
output_event = group_leader;
@@ -12750,7 +12736,7 @@ SYSCALL_DEFINE5(perf_event_open,
task = find_lively_task_by_vpid(pid);
if (IS_ERR(task)) {
err = PTR_ERR(task);
goto err_group_fd;
goto err_fd;
}
}
@@ -13017,12 +13003,11 @@ SYSCALL_DEFINE5(perf_event_open,
mutex_unlock(&current->perf_event_mutex);
/*
* Drop the reference on the group_event after placing the
* new event on the sibling_list. This ensures destruction
* of the group leader will find the pointer to itself in
* perf_group_detach().
* File reference in group guarantees that group_leader has been
* kept alive until we place the new event on the sibling_list.
* This ensures destruction of the group leader will find
* the pointer to itself in perf_group_detach().
*/
fdput(group);
fd_install(event_fd, event_file);
return event_fd;
@@ -13041,8 +13026,6 @@ err_alloc:
err_task:
if (task)
put_task_struct(task);
err_group_fd:
fdput(group);
err_fd:
put_unused_fd(event_fd);
return err;