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untangling ep_call_nested(): and there was much rejoicing

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2020-08-22 23:13:27 -04:00
parent 99d84d4330
commit 773318eddb
1 changed files with 11 additions and 32 deletions
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43
fs/eventpoll.c
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@@ -439,25 +439,6 @@ static bool ep_push_nested(void *cookie)
return true; return true;
} }
/**
* ep_call_nested - Perform a bound (possibly) nested call, by checking
* that the recursion limit is not exceeded, and that
* the same nested call (by the meaning of same cookie) is
* no re-entered.
*
* @nproc: Nested call core function pointer.
* @priv: Opaque data to be passed to the @nproc callback.
* @cookie: Cookie to be used to identify this nested call.
*
* Returns: Returns the code returned by the @nproc callback, or -1 if
* the maximum recursion limit has been exceeded.
*/
static int ep_call_nested(int (*nproc)(void *, void *, int), void *priv,
void *cookie)
{
return (*nproc)(priv, cookie, nesting);
}
/* /*
* As described in commit 0ccf831cb lockdep: annotate epoll * As described in commit 0ccf831cb lockdep: annotate epoll
* the use of wait queues used by epoll is done in a very controlled * the use of wait queues used by epoll is done in a very controlled
@@ -1325,7 +1306,7 @@ static void path_count_init(void)
path_count[i] = 0; path_count[i] = 0;
} }
static int reverse_path_check_proc(void *priv, void *cookie, int call_nests) static int reverse_path_check_proc(void *priv, void *cookie, int depth)
{ {
int error = 0; int error = 0;
struct file *file = priv; struct file *file = priv;
@@ -1341,13 +1322,13 @@ static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
child_file = epi->ep->file; child_file = epi->ep->file;
if (is_file_epoll(child_file)) { if (is_file_epoll(child_file)) {
if (list_empty(&child_file->f_ep_links)) { if (list_empty(&child_file->f_ep_links)) {
if (path_count_inc(call_nests)) { if (path_count_inc(depth)) {
error = -1; error = -1;
break; break;
} }
} else { } else {
error = ep_call_nested(reverse_path_check_proc, error = reverse_path_check_proc(child_file, child_file,
child_file, child_file); depth + 1);
} }
if (error != 0) if (error != 0)
break; break;
@@ -1379,8 +1360,7 @@ static int reverse_path_check(void)
/* let's call this for all tfiles */ /* let's call this for all tfiles */
list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) { list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) {
path_count_init(); path_count_init();
error = ep_call_nested(reverse_path_check_proc, current_file, error = reverse_path_check_proc(current_file, current_file, 0);
current_file);
if (error) if (error)
break; break;
} }
@@ -1886,8 +1866,7 @@ send_events:
} }
/** /**
* ep_loop_check_proc - Callback function to be passed to the @ep_call_nested() * ep_loop_check_proc - verify that adding an epoll file inside another
* API, to verify that adding an epoll file inside another
* epoll structure, does not violate the constraints, in * epoll structure, does not violate the constraints, in
* terms of closed loops, or too deep chains (which can * terms of closed loops, or too deep chains (which can
* result in excessive stack usage). * result in excessive stack usage).
@@ -1900,7 +1879,7 @@ send_events:
* Returns: Returns zero if adding the epoll @file inside current epoll * Returns: Returns zero if adding the epoll @file inside current epoll
* structure @ep does not violate the constraints, or -1 otherwise. * structure @ep does not violate the constraints, or -1 otherwise.
*/ */
static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) static int ep_loop_check_proc(void *priv, void *cookie, int depth)
{ {
int error = 0; int error = 0;
struct file *file = priv; struct file *file = priv;
@@ -1912,7 +1891,7 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
if (!ep_push_nested(cookie)) /* limits recursion */ if (!ep_push_nested(cookie)) /* limits recursion */
return -1; return -1;
mutex_lock_nested(&ep->mtx, call_nests + 1); mutex_lock_nested(&ep->mtx, depth + 1);
ep->gen = loop_check_gen; ep->gen = loop_check_gen;
for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
epi = rb_entry(rbp, struct epitem, rbn); epi = rb_entry(rbp, struct epitem, rbn);
@@ -1920,8 +1899,8 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
ep_tovisit = epi->ffd.file->private_data; ep_tovisit = epi->ffd.file->private_data;
if (ep_tovisit->gen == loop_check_gen) if (ep_tovisit->gen == loop_check_gen)
continue; continue;
error = ep_call_nested(ep_loop_check_proc, epi->ffd.file, error = ep_loop_check_proc(epi->ffd.file, ep_tovisit,
ep_tovisit); depth + 1);
if (error != 0) if (error != 0)
break; break;
} else { } else {
@@ -1959,7 +1938,7 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
*/ */
static int ep_loop_check(struct eventpoll *ep, struct file *file) static int ep_loop_check(struct eventpoll *ep, struct file *file)
{ {
return ep_call_nested(ep_loop_check_proc, file, ep); return ep_loop_check_proc(file, ep, 0);
} }
static void clear_tfile_check_list(void) static void clear_tfile_check_list(void)