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setfont: Initialize data pointer when resetting font

PATCH Applied Yutao Zhang 2 participants 2 messages Dec 5, 2025 – Dec 7, 2025

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Yutao Zhang

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PATCH 1/1 setfont: Initialize data pointer when resetting font

From: Tommy-Zhang3759 <[email protected]>

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 <[email protected]>
---
 src/libkfont/kdfontop.c | 1 +
 1 file changed, 1 insertion(+)
src/libkfont/kdfontop.c +1 -0
index 8f132ff..4f1f0d2 100644
@@ -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");
Signature · 1 line
2.52.0
Applied
#1 lore raw
Quoted 11 lines · Yutao Zhang

From: Tommy-Zhang3759 <[email protected]>

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 <[email protected]>

Applied. Thanks!

Quoted 20 lines
---
 src/libkfont/kdfontop.c | 1 +
 1 file changed, 1 insertion(+)
src/libkfont/kdfontop.c +1 -0
index 8f132ff..4f1f0d2 100644
@@ -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");
Signature · 1 line
2.52.0
Signature · 1 line
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