[PATCH 6.19 271/311] vt: resize saved unicode buffer on alt screen exit after resize
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2026-04-08 19:01:27
Also in:
stable
6.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Nicolas Pitre <nico@fluxnic.net>
commit 3ddbea7542ae529c1a88ef9a8b1ce169126211f6 upstream.
Instead of discarding the saved unicode buffer when the console was
resized while in the alternate screen, resize it to the current
dimensions using vc_uniscr_copy_area() to preserve its content. This
properly restores the unicode screen on alt screen exit rather than
lazily rebuilding it from a lossy reverse glyph translation.
On allocation failure the stale buffer is freed and vc_uni_lines is
set to NULL so it gets lazily rebuilt via vc_uniscr_check() when next
needed.
Fixes: 40014493cece ("vt: discard stale unicode buffer on alt screen exit after resize")
Cc: stable <stable@kernel.org>
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Link: https://patch.msgid.link/3nsr334n-079q-125n-7807-n4nq818758ns@syhkavp.arg
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/vt/vt.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c@@ -1907,7 +1907,6 @@ static void leave_alt_screen(struct vc_d unsigned int rows = min(vc->vc_saved_rows, vc->vc_rows); unsigned int cols = min(vc->vc_saved_cols, vc->vc_cols); u16 *src, *dest; - bool uni_lines_stale; if (vc->vc_saved_screen == NULL) return; /* Not inside an alt-screen */
@@ -1918,16 +1917,23 @@ static void leave_alt_screen(struct vc_d } /* * If the console was resized while in the alternate screen, - * vc_saved_uni_lines was allocated for the old dimensions. - * Restoring it would cause out-of-bounds accesses. Discard it - * and let the unicode screen be lazily rebuilt. + * resize the saved unicode buffer to the current dimensions. + * On allocation failure new_uniscr is NULL, causing the old + * buffer to be freed and vc_uni_lines to be lazily rebuilt + * via vc_uniscr_check() when next needed. */ - uni_lines_stale = vc->vc_saved_rows != vc->vc_rows || - vc->vc_saved_cols != vc->vc_cols; - if (uni_lines_stale) + if (vc->vc_saved_uni_lines && + (vc->vc_saved_rows != vc->vc_rows || + vc->vc_saved_cols != vc->vc_cols)) { + u32 **new_uniscr = vc_uniscr_alloc(vc->vc_cols, vc->vc_rows); + + if (new_uniscr) + vc_uniscr_copy_area(new_uniscr, vc->vc_cols, vc->vc_rows, + vc->vc_saved_uni_lines, cols, 0, rows); vc_uniscr_free(vc->vc_saved_uni_lines); - else - vc_uniscr_set(vc, vc->vc_saved_uni_lines); + vc->vc_saved_uni_lines = new_uniscr; + } + vc_uniscr_set(vc, vc->vc_saved_uni_lines); vc->vc_saved_uni_lines = NULL; restore_cur(vc); /* Update the entire screen */