[PATCH 6.6 087/567] eventpoll: Fix integer overflow in ep_loop_check_proc()

Greg Kroah-Hartman
2026-03-23T14:55:44Z

6.6-stable review patch. If anyone has any objections, please let me know.

------------------

From: Jann Horn <jannh@google.com>

commit fdcfce93073d990ed4b71752e31ad1c1d6e9d58b upstream.

If a recursive call to ep_loop_check_proc() hits the `result = INT_MAX`,
an integer overflow will occur in the calling ep_loop_check_proc() at
`result = max(result, ep_loop_check_proc(ep_tovisit, depth + 1) + 1)`,
breaking the recursion depth check.

Fix it by using a different placeholder value that can't lead to an
overflow.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Fixes: f2e467a48287 ("eventpoll: Fix semi-unbounded recursion")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://patch.msgid.link/20260223-epoll-int-overflow-v1-1-452f35132224@google.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/eventpoll.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1907,7 +1907,8 @@ static int ep_poll(struct eventpoll *ep,
* @ep: the &struct eventpoll to be currently checked.
* @depth: Current depth of the path being checked.
*
- * Return: depth of the subtree, or INT_MAX if we found a loop or went too deep.
+ * Return: depth of the subtree, or a value bigger than EP_MAX_NESTS if we found
+ * a loop or went too deep.
*/
static int ep_loop_check_proc(struct eventpoll *ep, int depth)
{
@@ -1926,7 +1927,7 @@ static int ep_loop_check_proc(struct eve
struct eventpoll *ep_tovisit;
ep_tovisit = epi->ffd.file->private_data;
if (ep_tovisit == inserting_into || depth > EP_MAX_NESTS)
- result = INT_MAX;
+ result = EP_MAX_NESTS+1;
else
result = max(result, ep_loop_check_proc(ep_tovisit, depth + 1) + 1);
if (result > EP_MAX_NESTS)