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Message-Id: <20211124115716.137070329@linuxfoundation.org>
Date: Wed, 24 Nov 2021 12:56:51 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Geert Uytterhoeven <geert@...ux-m68k.org>,
Miguel Ojeda <ojeda@...nel.org>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 169/251] auxdisplay: img-ascii-lcd: Fix lock-up when displaying empty string
From: Geert Uytterhoeven <geert@...ux-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@...ux-m68k.org>
Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.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;
--
2.33.0
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