[PATCH 6.12 026/113] binderfs: fix ida_alloc_max() upper bound

Greg Kroah-Hartman
2026-02-09T14:37:19Z

From: Carlos Llamas <cmllamas@google.com>

commit ec4ddc90d201d09ef4e4bef8a2c6d9624525ad68 upstream.

The 'max' argument of ida_alloc_max() takes the maximum valid ID and not
the "count". Using an ID of BINDERFS_MAX_MINOR (1 << 20) for dev->minor
would exceed the limits of minor numbers (20-bits). Fix this off-by-one
error by subtracting 1 from the 'max'.

Cc: stable@vger.kernel.org
Fixes: 3ad20fe393b3 ("binder: implement binderfs")
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://patch.msgid.link/20260127235545.2307876-2-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/android/binderfs.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -131,8 +131,8 @@ static int binderfs_binder_device_create
mutex_lock(&binderfs_minors_mutex);
if (++info->device_count <= info->mount_opts.max)
minor = ida_alloc_max(&binderfs_minors,
- use_reserve ? BINDERFS_MAX_MINOR :
- BINDERFS_MAX_MINOR_CAPPED,
+ use_reserve ? BINDERFS_MAX_MINOR - 1 :
+ BINDERFS_MAX_MINOR_CAPPED - 1,
GFP_KERNEL);
else
minor = -ENOSPC;
@@ -422,8 +422,8 @@ static int binderfs_binder_ctl_create(st
/* Reserve a new minor number for the new device. */
mutex_lock(&binderfs_minors_mutex);
minor = ida_alloc_max(&binderfs_minors,
- use_reserve ? BINDERFS_MAX_MINOR :
- BINDERFS_MAX_MINOR_CAPPED,
+ use_reserve ? BINDERFS_MAX_MINOR - 1 :
+ BINDERFS_MAX_MINOR_CAPPED - 1,
GFP_KERNEL);
mutex_unlock(&binderfs_minors_mutex);
if (minor < 0) {