2021-07-10 16:50:41

by Salah Triki

Subject: [PATCH] dax: replace sprintf() by scnprintf()

Replace sprintf() by scnprintf() in order to avoid buffer overflows.

Signed-off-by: Salah Triki <[email protected]>
---
drivers/dax/bus.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 5aee26e1bbd6..bcae4be6ae76 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -76,7 +76,7 @@ static ssize_t do_id_store(struct device_driver *drv, const char *buf,
fields = sscanf(buf, "dax%d.%d", &region_id, &id);
if (fields != 2)
return -EINVAL;
- sprintf(devname, "dax%d.%d", region_id, id);
+ scnprintf(devname, DAX_NAME_LEN, "dax%d.%d", region_id, id);
if (!sysfs_streq(buf, devname))
return -EINVAL;

--
2.25.1

2021-07-10 17:05:40

by Joe Perches

Subject: Re: [PATCH] dax: replace sprintf() by scnprintf()

On Sat, 2021-07-10 at 17:46 +0100, Salah Triki wrote:
> Replace sprintf() by scnprintf() in order to avoid buffer overflows.

OK but also not strictly necessary. DAX_NAME_LEN is 30.

Are you finding and changing these manually or with a script?

> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
[]
> @@ -76,7 +76,7 @@ static ssize_t do_id_store(struct device_driver *drv, const char *buf,
> ? fields = sscanf(buf, "dax%d.%d", &region_id, &id);
> ? if (fields != 2)
> ? return -EINVAL;
> - sprintf(devname, "dax%d.%d", region_id, id);
> + scnprintf(devname, DAX_NAME_LEN, "dax%d.%d", region_id, id);
> ? if (!sysfs_streq(buf, devname))
> ? return -EINVAL;
> ?
>

2021-07-12 12:27:56

by Salah Triki

Subject: Re: [PATCH] dax: replace sprintf() by scnprintf()

On Sat, Jul 10, 2021 at 10:04:48AM -0700, Joe Perches wrote:
> On Sat, 2021-07-10 at 17:46 +0100, Salah Triki wrote:
> > Replace sprintf() by scnprintf() in order to avoid buffer overflows.
>
> OK but also not strictly necessary. DAX_NAME_LEN is 30.
>
> Are you finding and changing these manually or with a script?
>
> > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> []
> > @@ -76,7 +76,7 @@ static ssize_t do_id_store(struct device_driver *drv, const char *buf,
> > ? fields = sscanf(buf, "dax%d.%d", &region_id, &id);
> > ? if (fields != 2)
> > ? return -EINVAL;
> > - sprintf(devname, "dax%d.%d", region_id, id);
> > + scnprintf(devname, DAX_NAME_LEN, "dax%d.%d", region_id, id);
> > ? if (!sysfs_streq(buf, devname))
> > ? return -EINVAL;
> > ?
> >
>
>

since region_id and id are unsigned long may be devname should be
char[21].

I'm finding and changing these manually.

Thanx

2021-07-12 16:15:49

by Joe Perches

Subject: Re: [PATCH] dax: replace sprintf() by scnprintf()

On Mon, 2021-07-12 at 13:26 +0100, Salah Triki wrote:
> On Sat, Jul 10, 2021 at 10:04:48AM -0700, Joe Perches wrote:
> > On Sat, 2021-07-10 at 17:46 +0100, Salah Triki wrote:
> > > Replace sprintf() by scnprintf() in order to avoid buffer overflows.
> >
> > OK but also not strictly necessary. DAX_NAME_LEN is 30.
> >
> > Are you finding and changing these manually or with a script?
> >
> > > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> > []
> > > @@ -76,7 +76,7 @@ static ssize_t do_id_store(struct device_driver *drv, const char *buf,
> > > ? fields = sscanf(buf, "dax%d.%d", &region_id, &id);
> > > ? if (fields != 2)
> > > ? return -EINVAL;
> > > - sprintf(devname, "dax%d.%d", region_id, id);
> > > + scnprintf(devname, DAX_NAME_LEN, "dax%d.%d", region_id, id);
> > > ? if (!sysfs_streq(buf, devname))
> > > ? return -EINVAL;
> > > ?
> > >
> >
> >
>
> since region_id and id are unsigned long may be devname should be
> char[21].

I think you need to look at the code a bit more carefully.

unsigned int region_id, id;

Also the output is %d, so the maximum length of each output
int is 10 with a possible leading minus sign.

3 + 10 + 1 + 10 + 1. So 25 not 21 which is too small.

The %d uses could be changed to %u to make it 23.
But really it hardly matters as 30 is sufficent and the
function call depth here isn't particularly high.

> I'm finding and changing these manually.

coccinelle could help.
https://coccinelle.gitlabpages.inria.fr/website/

2021-07-12 16:50:23

by Salah Triki

Subject: Re: [PATCH] dax: replace sprintf() by scnprintf()

On Mon, Jul 12, 2021 at 09:14:53AM -0700, Joe Perches wrote:
> On Mon, 2021-07-12 at 13:26 +0100, Salah Triki wrote:
> > On Sat, Jul 10, 2021 at 10:04:48AM -0700, Joe Perches wrote:
> > > On Sat, 2021-07-10 at 17:46 +0100, Salah Triki wrote:
> > > > Replace sprintf() by scnprintf() in order to avoid buffer overflows.
> > >
> > > OK but also not strictly necessary. DAX_NAME_LEN is 30.
> > >
> > > Are you finding and changing these manually or with a script?
> > >
> > > > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> > > []
> > > > @@ -76,7 +76,7 @@ static ssize_t do_id_store(struct device_driver *drv, const char *buf,
> > > > ? fields = sscanf(buf, "dax%d.%d", &region_id, &id);
> > > > ? if (fields != 2)
> > > > ? return -EINVAL;
> > > > - sprintf(devname, "dax%d.%d", region_id, id);
> > > > + scnprintf(devname, DAX_NAME_LEN, "dax%d.%d", region_id, id);
> > > > ? if (!sysfs_streq(buf, devname))
> > > > ? return -EINVAL;
> > > > ?
> > > >
> > >
> > >
> >
> > since region_id and id are unsigned long may be devname should be
> > char[21].
>
> I think you need to look at the code a bit more carefully.
>
> unsigned int region_id, id;
>
> Also the output is %d, so the maximum length of each output
> int is 10 with a possible leading minus sign.
>
> 3 + 10 + 1 + 10 + 1. So 25 not 21 which is too small.
>
> The %d uses could be changed to %u to make it 23.
> But really it hardly matters as 30 is sufficent and the
> function call depth here isn't particularly high.
>
> > I'm finding and changing these manually.
>
> coccinelle could help.
> https://coccinelle.gitlabpages.inria.fr/website/
>
>

Thanx