| From bbe43bef65c2b9d1e97ed243f29667f8fe442859 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Tue, 19 Oct 2021 16:45:02 +0200 |
| Subject: auxdisplay: img-ascii-lcd: Fix lock-up when displaying empty string |
| |
| 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 efb928e25aef3..9556d6827f005 100644 |
| --- a/drivers/auxdisplay/img-ascii-lcd.c |
| +++ b/drivers/auxdisplay/img-ascii-lcd.c |
| @@ -280,6 +280,16 @@ 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; |
| -- |
| 2.33.0 |
| |
