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| author | Geert Uytterhoeven <geert@linux-m68k.org> | 2021-10-19 16:45:02 +0200 |
|---|---|---|
| committer | Miguel Ojeda <ojeda@kernel.org> | 2021-10-21 23:36:28 +0200 |
| commit | afcb5a811ff3ab3969f09666535eb6018a160358 (patch) | |
| tree | 2a6d3c09e4975adfa8ab343171a500f5eb9ff40b /drivers/auxdisplay | |
| parent | ae53c6963f5a3dc89dd04fa1372910e442fabc14 (diff) | |
| download | linux-stable-afcb5a811ff3ab3969f09666535eb6018a160358.tar.gz linux-stable-afcb5a811ff3ab3969f09666535eb6018a160358.tar.bz2 linux-stable-afcb5a811ff3ab3969f09666535eb6018a160358.zip | |
auxdisplay: img-ascii-lcd: Fix lock-up when displaying empty string
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>
Diffstat (limited to 'drivers/auxdisplay')
| -rw-r--r-- | drivers/auxdisplay/img-ascii-lcd.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/auxdisplay/img-ascii-lcd.c b/drivers/auxdisplay/img-ascii-lcd.c index 1cce409ce5ca..e33ce0151cdf 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; |