CVE-2025-37814 — tty: Require CAP_SYS_ADMIN for all usages of TIOCL_SELMOUSEREPORT

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

tty: Require CAP_SYS_ADMIN for all usages of TIOCL_SELMOUSEREPORT

This requirement was overeagerly loosened in commit 2f83e38a095f ("tty: Permit some TIOCL_SETSEL modes without CAP_SYS_ADMIN"), but as it turns out,

(1) the logic I implemented there was inconsistent (apologies!),

(2) TIOCL_SELMOUSEREPORT might actually be a small security risk after all, and

(3) TIOCL_SELMOUSEREPORT is only meant to be used by the mouse daemon (GPM or Consolation), which runs as CAP_SYS_ADMIN already.

In more detail:

1. The previous patch has inconsistent logic:

In commit 2f83e38a095f ("tty: Permit some TIOCL_SETSEL modes without CAP_SYS_ADMIN"), we checked for sel_mode == TIOCL_SELMOUSEREPORT, but overlooked that the lower four bits of this "mode" parameter were actually used as an additional way to pass an argument. So the patch did actually still require CAP_SYS_ADMIN, if any of the mouse button bits are set, but did not require it if none of the mouse buttons bits are set.

This logic is inconsistent and was not intentional. We should have the same policies for using TIOCL_SELMOUSEREPORT independent of the value of the "hidden" mouse button argument.

I sent a separate documentation patch to the man page list with more details on TIOCL_SELMOUSEREPORT: https://lore.kernel.org/all/20250223091342.35523-2-gnoack3000@gmail.com/

2. TIOCL_SELMOUSEREPORT is…

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CVE-2025-37814 — tty: Require CAP_SYS_ADMIN for all usages of TIOCL_SELMOUSEREPORT