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DKIM_TRACE(0.00)[suse.de:+] X-Spam-Flag: NO Am 28.09.26 um 11:09 schrieb sashiko-bot@kernel.org: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [Low] vt: unprivileged log injection via pr_warn_once in cursor sizing FYI this is by intention. In DRM land, we usually allow for warn_once to be triggered by user-space code.  If that's not an option for vt, let's use pr_debug() instead. > -- > > commit 4874174842fbef217a6215957d5bf1bff1442b36 > Author: Thomas Zimmermann > > vt: Add cursor-size helpers > > The new helpers vc_cursor_start() and vc_cursor_end() return the scanlines > in which the cursor block starts respectively ends. Users can control the > cursor size with the vt module's parameter cur_default or with the ESC > sequence \e[?Nc. In case of an invalid setting, the new helpers fall back > to cur_default and then underline cursors. > >> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c >> index 57edf37495a81..8141296ccad05 100644 >> --- a/drivers/tty/vt/vt.c >> +++ b/drivers/tty/vt/vt.c > [ ... ] > >> @@ -264,6 +265,109 @@ unsigned int vc_font_size(const struct vc_font *font) >> } >> EXPORT_SYMBOL_GPL(vc_font_size); >> >> +/* >> + * Cursors >> + */ >> + >> +static unsigned int vc_cursor_size(unsigned int cursor_size) >> +{ >> + const unsigned int cursor_default_size = CUR_SIZE(READ_ONCE(cur_default)); >> + >> +retry: >> + switch (cursor_size) { >> + case CUR_NONE: >> + case CUR_UNDERLINE: >> + case CUR_LOWER_THIRD: >> + case CUR_LOWER_HALF: >> + case CUR_TWO_THIRDS: >> + case CUR_BLOCK: >> + return cursor_size; >> + default: >> + pr_warn_once("Unknown cursor %u\n", cursor_size); >> + fallthrough; > [Severity: Low] > Is it expected that an unprivileged user can trigger this warning message? > > An unprivileged user can write a specific DEC escape sequence (e.g., > \e[?103c) to the VT, which parses an unhandled size into > vc->vc_cursor_type via CSI_MAKE. > > When the console driver later updates the cursor, vc_cursor_size() hits > the default case and emits this warning. > > Since pr_warn_once() is rate-limited to once per boot, it cannot cause > a denial of service, but it still allows local unprivileged users with > write access to a VT to add a warning line to the kernel log. > >> + case CUR_DEF: >> + /* >> + * Use user-given default size, or underline if >> + * the given default is invalid. >> + */ >> + if (cursor_size != cursor_default_size) >> + cursor_size = cursor_default_size; >> + else >> + cursor_size = CUR_UNDERLINE; >> + goto retry; >> + } >> +} > [ ... ] > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)