The sysctl knob allows any user with SYS_ADMIN capability to
taint the kernel with any arbitrary value, but this might
produce an invalid flags bitset being committed to tainted_mask.
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, as well as
it makes clear use of TAINT_USER flag to mark the kernel
tainted by user everytime a taint value is written
to the kernel.tainted sysctl.
Signed-off-by: Rafael Aquini <aquini@xxxxxxxxxx>
---
kernel/sysctl.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8a176d8727a3..f0a4fb38ac62 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2623,17 +2623,32 @@ static int proc_taint(struct ctl_table *table, int write,
return err;
if (write) {
+ int i;
+
+ /*
+ * Ignore user input that would make us committing
+ * arbitrary invalid TAINT flags in the loop below.
+ */
+ tmptaint &= (1UL << TAINT_FLAGS_COUNT) - 1;
+
/*
* Poor man's atomic or. Not worth adding a primitive
* to everyone's atomic.h for this
*/
- int i;
for (i = 0; i < BITS_PER_LONG && tmptaint >> i; i++) {
if ((tmptaint >> i) & 1)
add_taint(i, LOCKDEP_STILL_OK);
}
+
+ /*
+ * Users with SYS_ADMIN capability can include any arbitrary
+ * taint flag by writing to this interface. If that's the case,
+ * we also need to mark the kernel "tainted by user".
+ */
+ add_taint(TAINT_USER, LOCKDEP_STILL_OK);
}
+
return err;
}
--
2.25.4
