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vcsa: clamp header values when they don't fit

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The /dev/vcsa* devices have a fixed char-sized header that stores the
screen geometry and cursor location. Let's make sure it doesn't contain
random garbage when those values exceed 255. If ever it becomes necessary
to convey larger screen info to user space then a larger header in the
not-yet-implemented /dev/vcsua* devices should be considered.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicolas Pitre
2019-01-08 22:55:02 -05:00
committed by Greg Kroah-Hartman
parent a5db482640
commit 8a08549431
2 changed files with 6 additions and 4 deletions
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5
drivers/tty/vt/vc_screen.c
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@@ -335,8 +335,9 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
if (p < HEADER_SIZE) {
size_t tmp_count;
con_buf0[0] = (char)vc->vc_rows;
con_buf0[1] = (char)vc->vc_cols;
/* clamp header values if they don't fit */
con_buf0[0] = min(vc->vc_rows, 0xFFu);
con_buf0[1] = min(vc->vc_cols, 0xFFu);
getconsxy(vc, con_buf0 + 2);
con_buf_start += p;