* [PATCH] media: bttv: Fix a NULL pointer dereference in bttv_s_fbuf()
@ 2022-01-24 17:04 Zhou Qingyang
2022-01-28 10:16 ` Greg KH
0 siblings, 1 reply; 2+ messages in thread
From: Zhou Qingyang @ 2022-01-24 17:04 UTC (permalink / raw)
To: zhou1615
Cc: kjlu, Mauro Carvalho Chehab, Zhen Lei, Laurent Pinchart,
Arnd Bergmann, Douglas Schilling Landgraf, linux-media,
linux-kernel
In bttv_s_fbuf(), the return value of videobuf_sg_alloc() is assigned
to variable new and there is a dereference of it after that. the return
value of videobuf_sg_alloc() could be NULL on failure of allocation,
which could lead to a NULL pointer dereference.
Fix this bug by adding a NULL check of new.
This bug was found by a static analyzer.
Builds with 'make allyesconfig' show no new warnings,
and our static analyzer no longer warns about this code
Fixes: 402aa76aa5e5 ("V4L/DVB (6911): Converted bttv to use video_ioctl2")
Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
---
The analysis employs differential checking to identify inconsistent
security operations (e.g., checks or kfrees) between two code paths
and confirms that the inconsistent operations are not recovered in the
current function or the callers, so they constitute bugs.
Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.
drivers/media/pci/bt8xx/bttv-driver.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/media/pci/bt8xx/bttv-driver.c b/drivers/media/pci/bt8xx/bttv-driver.c
index 5aa46593ddc6..c0664cffb881 100644
--- a/drivers/media/pci/bt8xx/bttv-driver.c
+++ b/drivers/media/pci/bt8xx/bttv-driver.c
@@ -2627,6 +2627,8 @@ static int bttv_s_fbuf(struct file *file, void *f,
struct bttv_buffer *new;
new = videobuf_sg_alloc(sizeof(*new));
+ if (!new)
+ return -ENOMEM;
new->crop = btv->crop[!!fh->do_crop].rect;
bttv_overlay_risc(btv, &fh->ov, fh->ovfmt, new);
retval = bttv_switch_overlay(btv, fh, new);
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] media: bttv: Fix a NULL pointer dereference in bttv_s_fbuf()
2022-01-24 17:04 [PATCH] media: bttv: Fix a NULL pointer dereference in bttv_s_fbuf() Zhou Qingyang
@ 2022-01-28 10:16 ` Greg KH
0 siblings, 0 replies; 2+ messages in thread
From: Greg KH @ 2022-01-28 10:16 UTC (permalink / raw)
To: Zhou Qingyang
Cc: kjlu, Mauro Carvalho Chehab, Zhen Lei, Laurent Pinchart,
Arnd Bergmann, Douglas Schilling Landgraf, linux-media,
linux-kernel
On Tue, Jan 25, 2022 at 01:04:09AM +0800, Zhou Qingyang wrote:
> In bttv_s_fbuf(), the return value of videobuf_sg_alloc() is assigned
> to variable new and there is a dereference of it after that. the return
> value of videobuf_sg_alloc() could be NULL on failure of allocation,
> which could lead to a NULL pointer dereference.
>
> Fix this bug by adding a NULL check of new.
>
> This bug was found by a static analyzer.
>
> Builds with 'make allyesconfig' show no new warnings,
> and our static analyzer no longer warns about this code
>
> Fixes: 402aa76aa5e5 ("V4L/DVB (6911): Converted bttv to use video_ioctl2")
> Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
> ---
> The analysis employs differential checking to identify inconsistent
> security operations (e.g., checks or kfrees) between two code paths
> and confirms that the inconsistent operations are not recovered in the
> current function or the callers, so they constitute bugs.
>
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
>
> drivers/media/pci/bt8xx/bttv-driver.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/media/pci/bt8xx/bttv-driver.c b/drivers/media/pci/bt8xx/bttv-driver.c
> index 5aa46593ddc6..c0664cffb881 100644
> --- a/drivers/media/pci/bt8xx/bttv-driver.c
> +++ b/drivers/media/pci/bt8xx/bttv-driver.c
> @@ -2627,6 +2627,8 @@ static int bttv_s_fbuf(struct file *file, void *f,
> struct bttv_buffer *new;
>
> new = videobuf_sg_alloc(sizeof(*new));
> + if (!new)
> + return -ENOMEM;
> new->crop = btv->crop[!!fh->do_crop].rect;
> bttv_overlay_risc(btv, &fh->ov, fh->ovfmt, new);
> retval = bttv_switch_overlay(btv, fh, new);
> --
> 2.25.1
>
As stated before, umn.edu is still not allowed to contribute to the
Linux kernel. Please work with your administration to resolve this
issue.
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2022-01-24 17:04 [PATCH] media: bttv: Fix a NULL pointer dereference in bttv_s_fbuf() Zhou Qingyang
2022-01-28 10:16 ` Greg KH
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