* [patch] ext4: underflow in alignment check
@ 2016-06-16 7:07 ` Dan Carpenter
0 siblings, 0 replies; 10+ messages in thread
From: Dan Carpenter @ 2016-06-16 7:07 UTC (permalink / raw)
To: Theodore Ts'o
Cc: Andreas Dilger, linux-ext4, linux-kernel, kernel-janitors
My static checker complains that this can underflow if arg is negative
which is true.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b1a3471..a2a17e9 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1576,7 +1576,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
} else if (token = Opt_min_batch_time) {
sbi->s_min_batch_time = arg;
} else if (token = Opt_inode_readahead_blks) {
- if (arg && (arg > (1 << 30) || !is_power_of_2(arg))) {
+ if (arg && (arg > (1U << 30) || !is_power_of_2(arg))) {
ext4_msg(sb, KERN_ERR,
"EXT4-fs: inode_readahead_blks must be "
"0 or a power of 2 smaller than 2^31");
^ permalink raw reply related [flat|nested] 10+ messages in thread* [patch] ext4: underflow in alignment check
@ 2016-06-16 7:07 ` Dan Carpenter
0 siblings, 0 replies; 10+ messages in thread
From: Dan Carpenter @ 2016-06-16 7:07 UTC (permalink / raw)
To: Theodore Ts'o
Cc: Andreas Dilger, linux-ext4, linux-kernel, kernel-janitors
My static checker complains that this can underflow if arg is negative
which is true.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b1a3471..a2a17e9 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1576,7 +1576,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
} else if (token == Opt_min_batch_time) {
sbi->s_min_batch_time = arg;
} else if (token == Opt_inode_readahead_blks) {
- if (arg && (arg > (1 << 30) || !is_power_of_2(arg))) {
+ if (arg && (arg > (1U << 30) || !is_power_of_2(arg))) {
ext4_msg(sb, KERN_ERR,
"EXT4-fs: inode_readahead_blks must be "
"0 or a power of 2 smaller than 2^31");
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [patch] ext4: underflow in alignment check
2016-06-16 7:07 ` Dan Carpenter
@ 2016-06-20 16:02 ` Jan Kara
-1 siblings, 0 replies; 10+ messages in thread
From: Jan Kara @ 2016-06-20 16:02 UTC (permalink / raw)
To: Dan Carpenter
Cc: Theodore Ts'o, Andreas Dilger, linux-ext4, linux-kernel,
kernel-janitors
On Thu 16-06-16 10:07:09, Dan Carpenter wrote:
> My static checker complains that this can underflow if arg is negative
> which is true.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
How come? (1 << 30) fits even into 32-bit signed type. So where's the
problem?
Honza
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index b1a3471..a2a17e9 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1576,7 +1576,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
> } else if (token = Opt_min_batch_time) {
> sbi->s_min_batch_time = arg;
> } else if (token = Opt_inode_readahead_blks) {
> - if (arg && (arg > (1 << 30) || !is_power_of_2(arg))) {
> + if (arg && (arg > (1U << 30) || !is_power_of_2(arg))) {
> ext4_msg(sb, KERN_ERR,
> "EXT4-fs: inode_readahead_blks must be "
> "0 or a power of 2 smaller than 2^31");
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [patch] ext4: underflow in alignment check
@ 2016-06-20 16:02 ` Jan Kara
0 siblings, 0 replies; 10+ messages in thread
From: Jan Kara @ 2016-06-20 16:02 UTC (permalink / raw)
To: Dan Carpenter
Cc: Theodore Ts'o, Andreas Dilger, linux-ext4, linux-kernel,
kernel-janitors
On Thu 16-06-16 10:07:09, Dan Carpenter wrote:
> My static checker complains that this can underflow if arg is negative
> which is true.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
How come? (1 << 30) fits even into 32-bit signed type. So where's the
problem?
Honza
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index b1a3471..a2a17e9 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1576,7 +1576,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
> } else if (token == Opt_min_batch_time) {
> sbi->s_min_batch_time = arg;
> } else if (token == Opt_inode_readahead_blks) {
> - if (arg && (arg > (1 << 30) || !is_power_of_2(arg))) {
> + if (arg && (arg > (1U << 30) || !is_power_of_2(arg))) {
> ext4_msg(sb, KERN_ERR,
> "EXT4-fs: inode_readahead_blks must be "
> "0 or a power of 2 smaller than 2^31");
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [patch] ext4: underflow in alignment check
2016-06-20 16:02 ` Jan Kara
@ 2016-06-20 19:53 ` Dan Carpenter
-1 siblings, 0 replies; 10+ messages in thread
From: Dan Carpenter @ 2016-06-20 19:53 UTC (permalink / raw)
To: Jan Kara
Cc: Theodore Ts'o, Andreas Dilger, linux-ext4, linux-kernel,
kernel-janitors
On Mon, Jun 20, 2016 at 06:02:04PM +0200, Jan Kara wrote:
> On Thu 16-06-16 10:07:09, Dan Carpenter wrote:
> > My static checker complains that this can underflow if arg is negative
> > which is true.
> >
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> How come? (1 << 30) fits even into 32-bit signed type. So where's the
> problem?
Bad changelog... I was talking about a different issue. I was casting
it to unsigned to take advantage of type promototion. Assume we have:
int arg = 1 << 31;
(arg > (1 << 30)) // <-- this is false
(arg > (1U << 30)) // <-- this is true so there is no underflow.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [patch] ext4: underflow in alignment check
@ 2016-06-20 19:53 ` Dan Carpenter
0 siblings, 0 replies; 10+ messages in thread
From: Dan Carpenter @ 2016-06-20 19:53 UTC (permalink / raw)
To: Jan Kara
Cc: Theodore Ts'o, Andreas Dilger, linux-ext4, linux-kernel,
kernel-janitors
On Mon, Jun 20, 2016 at 06:02:04PM +0200, Jan Kara wrote:
> On Thu 16-06-16 10:07:09, Dan Carpenter wrote:
> > My static checker complains that this can underflow if arg is negative
> > which is true.
> >
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> How come? (1 << 30) fits even into 32-bit signed type. So where's the
> problem?
Bad changelog... I was talking about a different issue. I was casting
it to unsigned to take advantage of type promototion. Assume we have:
int arg = 1 << 31;
(arg > (1 << 30)) // <-- this is false
(arg > (1U << 30)) // <-- this is true so there is no underflow.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [patch] ext4: underflow in alignment check
2016-06-20 19:53 ` Dan Carpenter
@ 2016-06-21 7:43 ` Jan Kara
-1 siblings, 0 replies; 10+ messages in thread
From: Jan Kara @ 2016-06-21 7:43 UTC (permalink / raw)
To: Dan Carpenter
Cc: Jan Kara, Theodore Ts'o, Andreas Dilger, linux-ext4,
linux-kernel, kernel-janitors
On Mon 20-06-16 22:53:26, Dan Carpenter wrote:
> On Mon, Jun 20, 2016 at 06:02:04PM +0200, Jan Kara wrote:
> > On Thu 16-06-16 10:07:09, Dan Carpenter wrote:
> > > My static checker complains that this can underflow if arg is negative
> > > which is true.
> > >
> > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> >
> > How come? (1 << 30) fits even into 32-bit signed type. So where's the
> > problem?
>
> Bad changelog... I was talking about a different issue. I was casting
> it to unsigned to take advantage of type promototion. Assume we have:
>
> int arg = 1 << 31;
>
> (arg > (1 << 30)) // <-- this is false
> (arg > (1U << 30)) // <-- this is true so there is no underflow.
I see, but match_int() - or more precisely match_number() returns -ERANGE
when the number is > INT_MAX, subsequently we check whether the number is <
0 (Opt_inode_readahead_blks has flag MOPT_GTE0 set) and bail out if yes. So
at the place you are modifying we are sure the number is in [0, INT_MAX].
So the condition (arg > (1 << 30)) is pointless - just defensive
programming in case we decide e.g. to upgrade the type of 'arg' to long - but
not wrong...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [patch] ext4: underflow in alignment check
@ 2016-06-21 7:43 ` Jan Kara
0 siblings, 0 replies; 10+ messages in thread
From: Jan Kara @ 2016-06-21 7:43 UTC (permalink / raw)
To: Dan Carpenter
Cc: Jan Kara, Theodore Ts'o, Andreas Dilger, linux-ext4,
linux-kernel, kernel-janitors
On Mon 20-06-16 22:53:26, Dan Carpenter wrote:
> On Mon, Jun 20, 2016 at 06:02:04PM +0200, Jan Kara wrote:
> > On Thu 16-06-16 10:07:09, Dan Carpenter wrote:
> > > My static checker complains that this can underflow if arg is negative
> > > which is true.
> > >
> > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> >
> > How come? (1 << 30) fits even into 32-bit signed type. So where's the
> > problem?
>
> Bad changelog... I was talking about a different issue. I was casting
> it to unsigned to take advantage of type promototion. Assume we have:
>
> int arg = 1 << 31;
>
> (arg > (1 << 30)) // <-- this is false
> (arg > (1U << 30)) // <-- this is true so there is no underflow.
I see, but match_int() - or more precisely match_number() returns -ERANGE
when the number is > INT_MAX, subsequently we check whether the number is <
0 (Opt_inode_readahead_blks has flag MOPT_GTE0 set) and bail out if yes. So
at the place you are modifying we are sure the number is in [0, INT_MAX].
So the condition (arg > (1 << 30)) is pointless - just defensive
programming in case we decide e.g. to upgrade the type of 'arg' to long - but
not wrong...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [patch] ext4: underflow in alignment check
2016-06-21 7:43 ` Jan Kara
@ 2016-06-21 13:06 ` Dan Carpenter
-1 siblings, 0 replies; 10+ messages in thread
From: Dan Carpenter @ 2016-06-21 13:06 UTC (permalink / raw)
To: Jan Kara
Cc: Theodore Ts'o, Andreas Dilger, linux-ext4, linux-kernel,
kernel-janitors
On Tue, Jun 21, 2016 at 09:43:53AM +0200, Jan Kara wrote:
> On Mon 20-06-16 22:53:26, Dan Carpenter wrote:
> > On Mon, Jun 20, 2016 at 06:02:04PM +0200, Jan Kara wrote:
> > > On Thu 16-06-16 10:07:09, Dan Carpenter wrote:
> > > > My static checker complains that this can underflow if arg is negative
> > > > which is true.
> > > >
> > > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > >
> > > How come? (1 << 30) fits even into 32-bit signed type. So where's the
> > > problem?
> >
> > Bad changelog... I was talking about a different issue. I was casting
> > it to unsigned to take advantage of type promototion. Assume we have:
> >
> > int arg = 1 << 31;
> >
> > (arg > (1 << 30)) // <-- this is false
> > (arg > (1U << 30)) // <-- this is true so there is no underflow.
>
> I see, but match_int() - or more precisely match_number() returns -ERANGE
> when the number is > INT_MAX, subsequently we check whether the number is <
> 0 (Opt_inode_readahead_blks has flag MOPT_GTE0 set) and bail out if yes. So
> at the place you are modifying we are sure the number is in [0, INT_MAX].
> So the condition (arg > (1 << 30)) is pointless - just defensive
> programming in case we decide e.g. to upgrade the type of 'arg' to long - but
> not wrong...
Ah. Smatch wasn't able to figure out that MOPT_GTE0 was set.
Thanks for reviewing this.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [patch] ext4: underflow in alignment check
@ 2016-06-21 13:06 ` Dan Carpenter
0 siblings, 0 replies; 10+ messages in thread
From: Dan Carpenter @ 2016-06-21 13:06 UTC (permalink / raw)
To: Jan Kara
Cc: Theodore Ts'o, Andreas Dilger, linux-ext4, linux-kernel,
kernel-janitors
On Tue, Jun 21, 2016 at 09:43:53AM +0200, Jan Kara wrote:
> On Mon 20-06-16 22:53:26, Dan Carpenter wrote:
> > On Mon, Jun 20, 2016 at 06:02:04PM +0200, Jan Kara wrote:
> > > On Thu 16-06-16 10:07:09, Dan Carpenter wrote:
> > > > My static checker complains that this can underflow if arg is negative
> > > > which is true.
> > > >
> > > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > >
> > > How come? (1 << 30) fits even into 32-bit signed type. So where's the
> > > problem?
> >
> > Bad changelog... I was talking about a different issue. I was casting
> > it to unsigned to take advantage of type promototion. Assume we have:
> >
> > int arg = 1 << 31;
> >
> > (arg > (1 << 30)) // <-- this is false
> > (arg > (1U << 30)) // <-- this is true so there is no underflow.
>
> I see, but match_int() - or more precisely match_number() returns -ERANGE
> when the number is > INT_MAX, subsequently we check whether the number is <
> 0 (Opt_inode_readahead_blks has flag MOPT_GTE0 set) and bail out if yes. So
> at the place you are modifying we are sure the number is in [0, INT_MAX].
> So the condition (arg > (1 << 30)) is pointless - just defensive
> programming in case we decide e.g. to upgrade the type of 'arg' to long - but
> not wrong...
Ah. Smatch wasn't able to figure out that MOPT_GTE0 was set.
Thanks for reviewing this.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2016-06-21 13:06 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2016-06-16 7:07 [patch] ext4: underflow in alignment check Dan Carpenter
2016-06-16 7:07 ` Dan Carpenter
2016-06-20 16:02 ` Jan Kara
2016-06-20 16:02 ` Jan Kara
2016-06-20 19:53 ` Dan Carpenter
2016-06-20 19:53 ` Dan Carpenter
2016-06-21 7:43 ` Jan Kara
2016-06-21 7:43 ` Jan Kara
2016-06-21 13:06 ` Dan Carpenter
2016-06-21 13:06 ` Dan Carpenter
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