| Message ID | 20250508130612.82270-2-markus.burri@mt.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v4,1/6] iio: backend: fix out-of-bound write | expand |
On Sun, 11 May 2025 15:27:07 +0100 Jonathan Cameron <jic23@kernel.org> wrote: > On Thu, 8 May 2025 15:06:07 +0200 > Markus Burri <markus.burri@mt.com> wrote: > > > The buffer is set to 80 character. If a caller write more characters, > > count is truncated to the max available space in "simple_write_to_buffer". > > But afterwards a string terminator is written to the buffer at offset count > > without boundary check. The zero termination is written OUT-OF-BOUND. > > > > Add a check that the given buffer is smaller then the buffer to prevent. > > > > Fixes: 035b4989211d ("iio: backend: make sure to NULL terminate stack buffer") > > Signed-off-by: Markus Burri <markus.burri@mt.com> > I'm looking for a tag from Nuno on this one before applying. Please make sure to pick up tags on earlier versions. Nuno had sent a RB for this one which I've now added. People don't tend to look again at patches that they've already tagged so Nuno probably didn't see my ask for a tag above. Anyhow, now applied but will have to wait for a rebase of my fixes-togreg tree on rc1 once available. Thanks, Jonathan > > J > > --- > > drivers/iio/industrialio-backend.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c > > index a43c8d1bb3d0..31fe793e345e 100644 > > --- a/drivers/iio/industrialio-backend.c > > +++ b/drivers/iio/industrialio-backend.c > > @@ -155,11 +155,14 @@ static ssize_t iio_backend_debugfs_write_reg(struct file *file, > > ssize_t rc; > > int ret; > > > > + if (count >= sizeof(buf)) > > + return -ENOSPC; > > + > > rc = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf, count); > > if (rc < 0) > > return rc; > > > > - buf[count] = '\0'; > > + buf[rc] = '\0'; > > > > ret = sscanf(buf, "%i %i", &back->cached_reg_addr, &val); > > > >
diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c index a43c8d1bb3d0..31fe793e345e 100644 --- a/drivers/iio/industrialio-backend.c +++ b/drivers/iio/industrialio-backend.c @@ -155,11 +155,14 @@ static ssize_t iio_backend_debugfs_write_reg(struct file *file, ssize_t rc; int ret; + if (count >= sizeof(buf)) + return -ENOSPC; + rc = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf, count); if (rc < 0) return rc; - buf[count] = '\0'; + buf[rc] = '\0'; ret = sscanf(buf, "%i %i", &back->cached_reg_addr, &val);
The buffer is set to 80 character. If a caller write more characters, count is truncated to the max available space in "simple_write_to_buffer". But afterwards a string terminator is written to the buffer at offset count without boundary check. The zero termination is written OUT-OF-BOUND. Add a check that the given buffer is smaller then the buffer to prevent. Fixes: 035b4989211d ("iio: backend: make sure to NULL terminate stack buffer") Signed-off-by: Markus Burri <markus.burri@mt.com> --- drivers/iio/industrialio-backend.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)