lkml.org 
[lkml]   [2022]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] binderfs: Fix the maximum minor value in binderfs_binder_device_create() and binderfs_binder_ctl_create()
Date
ida_alloc_max(..., max, ...) returns values from 0 to max, inclusive.

So, BINDERFS_MAX_MINOR is a valid value for 'minor'.

BINDERFS_MAX_MINOR is '1U << MINORBITS' and we have:
#define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi))

So, When this value is used in MKDEV() and it will overflow.

Fixes: 3ad20fe393b3 ("binder: implement binderfs")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
This patch is completely speculative.

The 'BINDERFS_MAX_MINOR_CAPPED - 1' is here only for symmetry with the
BINDERFS_MAX_MINOR case. I'm not sure at all that is is needed and, more
importantly, that it is correct.
---
drivers/android/binderfs.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index e3605cdd4335..47df1f381150 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -130,8 +130,8 @@ 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;
@@ -433,8 +433,8 @@ 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) {
--
2.32.0
\
 
 \ /
  Last update: 2022-03-27 13:19    [W:0.079 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site