[PATCH 1/2] rust_binderfs: fix ida_alloc_max() upper bound
From: Carlos Llamas
Date: Tue Jan 27 2026 - 18:56:05 EST
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@xxxxxxxxxxxxxxx
Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/r/202512181203.IOv6IChH-lkp@xxxxxxxxx/
Signed-off-by: Carlos Llamas <cmllamas@xxxxxxxxxx>
---
drivers/android/binder/rust_binderfs.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/android/binder/rust_binderfs.c b/drivers/android/binder/rust_binderfs.c
index c69026df775c..88374b31ab7c 100644
--- a/drivers/android/binder/rust_binderfs.c
+++ b/drivers/android/binder/rust_binderfs.c
@@ -132,8 +132,8 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
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;
@@ -405,8 +405,8 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
/* 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) {
--
2.52.0.457.g6b5491de43-goog