Commit e77132e7 authored by Rafael Aquini's avatar Rafael Aquini Committed by Linus Torvalds
Browse files

kernel/sysctl.c: ignore out-of-range taint bits introduced via kernel.tainted 



Users with SYS_ADMIN capability can add arbitrary taint flags to the
running kernel by writing to /proc/sys/kernel/tainted or issuing the
command 'sysctl -w kernel.tainted=...'.  This interface, however, is
open for any integer value and this might cause an invalid set of flags
being committed to the tainted_mask bitset.

This patch introduces a simple way for proc_taint() to ignore any
eventual invalid bit coming from the user input before committing those
bits to the kernel tainted_mask.

Signed-off-by: default avatarRafael Aquini <aquini@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Link: http://lkml.kernel.org/r/20200512223946.888020-1-aquini@redhat.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 60c958d8

kernel/sysctl.c

+2 −3
Original line number Diff line number Diff line
@@ -880,11 +880,10 @@ static int proc_taint(struct ctl_table *table, int write, 
		 * Poor man's atomic or. Not worth adding a primitive

		 * to everyone's atomic.h for this

		 */

		for (i = 0; i < BITS_PER_LONG && tmptaint >> i; i++) {

			if ((tmptaint >> i) & 1)

		for (i = 0; i < TAINT_FLAGS_COUNT; i++)

			if ((1UL << i) & tmptaint)

				add_taint(i, LOCKDEP_STILL_OK);

	}

	}



	return err;

}