* [PATCH] binderfs: Fix the maximum minor value in binderfs_binder_device_create() and binderfs_binder_ctl_create()
@ 2022-03-27 11:18 Christophe JAILLET
2022-03-29 11:20 ` Christian Brauner
0 siblings, 1 reply; 3+ messages in thread
From: Christophe JAILLET @ 2022-03-27 11:18 UTC (permalink / raw)
To: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Christian Brauner,
Hridya Valsaraju, Suren Baghdasaryan
Cc: linux-kernel, kernel-janitors, Christophe JAILLET, Todd Kjos
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] binderfs: Fix the maximum minor value in binderfs_binder_device_create() and binderfs_binder_ctl_create()
2022-03-27 11:18 [PATCH] binderfs: Fix the maximum minor value in binderfs_binder_device_create() and binderfs_binder_ctl_create() Christophe JAILLET
@ 2022-03-29 11:20 ` Christian Brauner
2022-03-31 20:35 ` Christophe JAILLET
0 siblings, 1 reply; 3+ messages in thread
From: Christian Brauner @ 2022-03-29 11:20 UTC (permalink / raw)
To: Christophe JAILLET
Cc: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Hridya Valsaraju,
Suren Baghdasaryan, linux-kernel, kernel-janitors, Todd Kjos
On Sun, Mar 27, 2022 at 01:18:17PM +0200, Christophe JAILLET wrote:
> 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.
Hm, since we're "removing" one alloctable device for the initial ipc
namespace, I think we need the -1 for the capped value.
Though I wonder if the simpler fix wouldn't just be to:
#define BINDERFS_MAX_MINOR MINORMASK
since include/linux/kdev_t.h has:
#define MINORBITS 20
#define MINORMASK ((1U << MINORBITS) - 1)
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] binderfs: Fix the maximum minor value in binderfs_binder_device_create() and binderfs_binder_ctl_create()
2022-03-29 11:20 ` Christian Brauner
@ 2022-03-31 20:35 ` Christophe JAILLET
0 siblings, 0 replies; 3+ messages in thread
From: Christophe JAILLET @ 2022-03-31 20:35 UTC (permalink / raw)
To: Christian Brauner
Cc: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Hridya Valsaraju,
Suren Baghdasaryan, linux-kernel, kernel-janitors, Todd Kjos
Le 29/03/2022 à 13:20, Christian Brauner a écrit :
> On Sun, Mar 27, 2022 at 01:18:17PM +0200, Christophe JAILLET wrote:
>> 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.
>
> Hm, since we're "removing" one alloctable device for the initial ipc
> namespace, I think we need the -1 for the capped value.
>
> Though I wonder if the simpler fix wouldn't just be to:
>
> #define BINDERFS_MAX_MINOR MINORMASK
>
> since include/linux/kdev_t.h has:
>
> #define MINORBITS 20
> #define MINORMASK ((1U << MINORBITS) - 1)
>
Hi,
I mostly agree with you, but I don't have a strong opinion on the other
uses of BINDERFS_MAX_MINOR.
The ones related to 'max' values looks good to me, but I don't know the
implication for the one used in binderfs_make_inode() and in
init_binderfs().
I won't be able to help further here.
CJ
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-03-27 11:18 [PATCH] binderfs: Fix the maximum minor value in binderfs_binder_device_create() and binderfs_binder_ctl_create() Christophe JAILLET
2022-03-29 11:20 ` Christian Brauner
2022-03-31 20:35 ` Christophe JAILLET
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