[PATCH] spi: spidev_test: Fix buffer overflow in unescape()

[Geert Uytterhoeven]

Sometimes spidev_test crashes with:

*** Error in `spidev_test': munmap_chunk(): invalid pointer: 0x00022020 ***
Aborted

or just

Segmentation fault

This is due to transfer_escaped_string() miscalculating the required
size of the buffer by two bytes, causing a buffer overflow in unescape().

Move the misplaced closing parenthesis to fix this.

Signed-off-by: Geert Uytterhoeven <geert+...@glider.be>
Fixes: 30061915be6e3a2c ("spi: spidev_test: Added input buffer from the terminal")
Cc: <sta...@vger.kernel.org> # v4.5+
---
The bug is present in all kernels since v4.1, but in v4.5 the code was
changed, and the source file was moved.

The fix for older kernels is straight-forward, there's only a single
strlen() call in Documentation/spi/spidev_test.c:

- size = strlen(input_tx+1);
+ size = strlen(input_tx)+1;

If you want, I can send a patch against v4.4 (for v4.1..v4.4) later.
---
tools/spi/spidev_test.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/spi/spidev_test.c b/tools/spi/spidev_test.c
index 1eaa4de6605bd935..ffa9908f7eb6670e 100644
--- a/tools/spi/spidev_test.c
+++ b/tools/spi/spidev_test.c
@@ -285,7 +285,7 @@ static void parse_opts(int argc, char *argv[])

static void transfer_escaped_string(int fd, char *str)
{
- size_t size = strlen(str + 1);
+ size_t size = strlen(str) + 1;
uint8_t *tx;
uint8_t *rx;

--
1.9.1

[Geert Uytterhoeven]

Sometimes spidev_test crashes with:

*** Error in `spidev_test': munmap_chunk(): invalid pointer: 0x00022020 ***
Aborted

or just

Segmentation fault

This is due to transfer_escaped_string() miscalculating the required

size of the buffer by one byte, causing a buffer overflow in unescape().

Drop the bogus "+ 1" in the strlen() parameter to fix this.

Note that unescape() never copies the zero-terminator of the source
string, so it writes at most as many bytes as the length of the source
string.

Signed-off-by: Geert Uytterhoeven <geert+...@glider.be>
Fixes: 30061915be6e3a2c ("spi: spidev_test: Added input buffer from the terminal")
Cc: <sta...@vger.kernel.org> # v4.5+
---

v2:
- As unescape() doesn't copy the zero-terminator, it's an off-by-one
not off-by-two bug, and the "+ 1" should just be dropped.

The bug is present in all kernel sources since v4.1, but in v4.5 the

code was changed, and the source file was moved.

The fix for older kernels is straight-forward, there's only a single
strlen() call in Documentation/spi/spidev_test.c:

- size = strlen(input_tx+1);

+ size = strlen(input_tx);

If you want, I can send a patch against v4.4 (for v4.1..v4.4) later.
---
tools/spi/spidev_test.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/spi/spidev_test.c b/tools/spi/spidev_test.c

index 1eaa4de6605bd935..f046b77cfefe3056 100644

--- a/tools/spi/spidev_test.c
+++ b/tools/spi/spidev_test.c
@@ -285,7 +285,7 @@ static void parse_opts(int argc, char *argv[])

static void transfer_escaped_string(int fd, char *str)
{
- size_t size = strlen(str + 1);

+ size_t size = strlen(str);

[Geert Uytterhoeven]

On Thu, Sep 8, 2016 at 8:05 PM, Geert Uytterhoeven
<geert+...@glider.be> wrote:
> Sometimes spidev_test crashes with:
>
> *** Error in `spidev_test': munmap_chunk(): invalid pointer: 0x00022020 ***
> Aborted
>
> or just
>
> Segmentation fault
>
> This is due to transfer_escaped_string() miscalculating the required
> size of the buffer by two bytes, causing a buffer overflow in unescape().
>
> Move the misplaced closing parenthesis to fix this.

After one more night of sleep, I realized it's an off-by-one, not off-by-two
bug (unescape() doesn't copy the zero-terminator of the source string).

Will send v2 in a moment...

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

[Mark Brown]

The patch

spi: spidev_test: Fix buffer overflow in unescape()

has been applied to the spi tree at

git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

From 0278b34bf15f8d8a609595b15909cd8622dd64ca Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert+...@glider.be>
Date: Fri, 9 Sep 2016 09:02:51 +0200
Subject: [PATCH] spi: spidev_test: Fix buffer overflow in unescape()

Sometimes spidev_test crashes with:

*** Error in `spidev_test': munmap_chunk(): invalid pointer: 0x00022020 ***
Aborted

or just

Segmentation fault

This is due to transfer_escaped_string() miscalculating the required
size of the buffer by one byte, causing a buffer overflow in unescape().

Drop the bogus "+ 1" in the strlen() parameter to fix this.

Note that unescape() never copies the zero-terminator of the source
string, so it writes at most as many bytes as the length of the source
string.

Fixes: 30061915be6e3a2c (spi: spidev_test: Added input buffer from the terminal)
Signed-off-by: Geert Uytterhoeven <geert+...@glider.be>
Signed-off-by: Mark Brown <bro...@kernel.org>

Cc: <sta...@vger.kernel.org> # v4.5+
---

tools/spi/spidev_test.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/spi/spidev_test.c b/tools/spi/spidev_test.c

index 8a73d8185316..f3825b676e38 100644
--- a/tools/spi/spidev_test.c
+++ b/tools/spi/spidev_test.c
@@ -284,7 +284,7 @@ static void parse_opts(int argc, char *argv[])

static void transfer_escaped_string(int fd, char *str)
{
- size_t size = strlen(str + 1);
+ size_t size = strlen(str);
uint8_t *tx;
uint8_t *rx;

--

2.8.1