forked from Minki/linux
8ffb82094b
In con_font_set(), when we need to guess font height (for compat reasons?), the current approach uses multiple userspace fetches, i.e., get_user(tmp, &charmap[32*i+h-1]), to derive the height. This has two drawbacks: 1. performance: accessing userspace memory is less efficient than directly de-reference the byte 2. security: a more critical problem is that the height derived might not match with the actual font.data. This is because a user thread might race condition to change the memory of op->data after the op->height guessing but before the second fetch: font.data = memdup_user(op->data, size). Leaving font.height = 32 while the actual height is 1 or vice-versa. This patch tries to resolve both issues by re-locating the height guessing part after the font.data is fetched in. In this way, the userspace data is fetched in one shot and we directly dereference the font.data in kernel space to probe for the height. Signed-off-by: Meng Xu <mengxu.gatech@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| .. | ||
| .gitignore | ||
| consolemap.c | ||
| cp437.uni | ||
| defkeymap.c_shipped | ||
| defkeymap.map | ||
| keyboard.c | ||
| Makefile | ||
| selection.c | ||
| vc_screen.c | ||
| vt_ioctl.c | ||
| vt.c | ||