From: Geert Uytterhoeven geert@linux-m68k.org
[ Upstream commit afcb5a811ff3ab3969f09666535eb6018a160358 ]
While writing an empty string to a device attribute is a no-op, and thus does not need explicit safeguards, the user can still write a single newline to an attribute file:
echo > .../message
If that happens, img_ascii_lcd_display() trims the newline, yielding an empty string, and causing an infinite loop in img_ascii_lcd_scroll().
Fix this by adding a check for empty strings. Clear the display in case one is encountered.
Fixes: 0cad855fbd083ee5 ("auxdisplay: img-ascii-lcd: driver for simple ASCII LCD displays") Signed-off-by: Geert Uytterhoeven geert@linux-m68k.org Signed-off-by: Miguel Ojeda ojeda@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/auxdisplay/img-ascii-lcd.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/drivers/auxdisplay/img-ascii-lcd.c b/drivers/auxdisplay/img-ascii-lcd.c index 58403052514f0..4d57185037a0d 100644 --- a/drivers/auxdisplay/img-ascii-lcd.c +++ b/drivers/auxdisplay/img-ascii-lcd.c @@ -284,6 +284,16 @@ static int img_ascii_lcd_display(struct img_ascii_lcd_ctx *ctx, if (msg[count - 1] == '\n') count--;
+ if (!count) { + /* clear the LCD */ + devm_kfree(&ctx->pdev->dev, ctx->message); + ctx->message = NULL; + ctx->message_len = 0; + memset(ctx->curr, ' ', ctx->cfg->num_chars); + ctx->cfg->update(ctx); + return 0; + } + new_msg = devm_kmalloc(&ctx->pdev->dev, count + 1, GFP_KERNEL); if (!new_msg) return -ENOMEM;