[PATCH] setfont: Initialize data pointer when resetting font

[PATCH] setfont: Initialize data pointer when resetting font

[Yutao Zhang]

From: Tommy-Zhang3759 <tommyzhang4707@outlook.com>

When resetting the font to default, the `data` field in the
`console_font_op` structure must be explicitly set to NULL.

Previously, this field was left uninitialized. The kernel treats a
non-NULL `data` pointer as a pointer to a font name string. This caused
the ioctl to fail with -EFAULT (Bad address) because it attempted to
read from a garbage address.

Signed-off-by: Yutao Zhang <tommyzhang4707@outlook.com>
---
 src/libkfont/kdfontop.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/libkfont/kdfontop.c b/src/libkfont/kdfontop.c
index 8f132ff..4f1f0d2 100644
--- a/src/libkfont/kdfontop.c
+++ b/src/libkfont/kdfontop.c
@@ -46,6 +46,7 @@ kfont_restore_font(struct kfont_context *ctx, int fd)
 		return -1;
 
 	cfo.op = KD_FONT_OP_SET_DEFAULT;
+	cfo.data = NULL;
 
 	if (ioctl(fd, KDFONTOP, &cfo)) {
 		KFONT_ERR(ctx, "ioctl(KD_FONT_OP_SET_DEFAULT): %m");
-- 
2.52.0

Re: [PATCH] setfont: Initialize data pointer when resetting font

[Alexey Gladkov]

On Sat, Dec 06, 2025 at 05:18:43AM +1100, Yutao Zhang wrote:
> From: Tommy-Zhang3759 <tommyzhang4707@outlook.com>
> 
> When resetting the font to default, the `data` field in the
> `console_font_op` structure must be explicitly set to NULL.
> 
> Previously, this field was left uninitialized. The kernel treats a
> non-NULL `data` pointer as a pointer to a font name string. This caused
> the ioctl to fail with -EFAULT (Bad address) because it attempted to
> read from a garbage address.
> 
> Signed-off-by: Yutao Zhang <tommyzhang4707@outlook.com>

Applied. Thanks!

> ---
>  src/libkfont/kdfontop.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/src/libkfont/kdfontop.c b/src/libkfont/kdfontop.c
> index 8f132ff..4f1f0d2 100644
> --- a/src/libkfont/kdfontop.c
> +++ b/src/libkfont/kdfontop.c
> @@ -46,6 +46,7 @@ kfont_restore_font(struct kfont_context *ctx, int fd)
>  		return -1;
>  
>  	cfo.op = KD_FONT_OP_SET_DEFAULT;
> +	cfo.data = NULL;
>  
>  	if (ioctl(fd, KDFONTOP, &cfo)) {
>  		KFONT_ERR(ctx, "ioctl(KD_FONT_OP_SET_DEFAULT): %m");
> -- 
> 2.52.0
> 
> 

-- 
Rgrds, legion