[PATCH 6.6 112/396] speakup: Fix 8bit characters from direct synth

Greg Kroah-Hartman
2024-04-01T16:40:51Z

From: Samuel Thibault <samuel.thibault@ens-lyon.org>

[ Upstream commit b6c8dafc9d86eb77e502bb018ec4105e8d2fbf78 ]

When userland echoes 8bit characters to /dev/synth with e.g.

echo -e '\xe9' > /dev/synth

synth_write would get characters beyond 0x7f, and thus negative when
char is signed. When given to synth_buffer_add which takes a u16, this
would sign-extend and produce a U+ffxy character rather than U+xy.
Users thus get garbled text instead of accents in their output.

Let's fix this by making sure that we read unsigned characters.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Fixes: 89fc2ae80bb1 ("speakup: extend synth buffer to 16bit unicode characters")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240204155736.2oh4ot7tiaa2wpbh@begin
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/accessibility/speakup/synth.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/accessibility/speakup/synth.c b/drivers/accessibility/speakup/synth.c
index eea2a2fa4f015..45f9061031338 100644
--- a/drivers/accessibility/speakup/synth.c
+++ b/drivers/accessibility/speakup/synth.c
@@ -208,8 +208,10 @@ void spk_do_flush(void)
wake_up_process(speakup_task);
}

-void synth_write(const char *buf, size_t count)
+void synth_write(const char *_buf, size_t count)
{
+ const unsigned char *buf = (const unsigned char *) _buf;
+
while (count--)
synth_buffer_add(*buf++);
synth_start();
--
2.43.0