This is a note to let you know that I've just added the patch titled
bpf: take into account liveness when propagating precision
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-take-into-account-liveness-when-propagating-prec.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 249dab06d0e28e82767d05453e7a6decbacb814e
Author: Andrii Nakryiko <andrii@xxxxxxxxxx>
Date: Thu Mar 9 14:41:31 2023 -0800
bpf: take into account liveness when propagating precision
[ Upstream commit 52c2b005a3c18c565fc70cfd0ca49375f301e952 ]
When doing state comparison, if old state has register that is not
marked as REG_LIVE_READ, then we just skip comparison, regardless what's
the state of corresponing register in current state. This is because not
REG_LIVE_READ register is irrelevant for further program execution and
correctness. All good here.
But when we get to precision propagation, after two states were declared
equivalent, we don't take into account old register's liveness, and thus
attempt to propagate precision for register in current state even if
that register in old state was not REG_LIVE_READ anymore. This is bad,
because register in current state could be anything at all and this
could cause -EFAULT due to internal logic bugs.
Fix by taking into account REG_LIVE_READ liveness mark to keep the logic
in state comparison in sync with precision propagation.
Fixes: a3ce685dd01a ("bpf: fix precision tracking")
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230309224131.57449-1-andrii@xxxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 37d4b5f5ec0c3..8e6f868d6cb9b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10616,7 +10616,8 @@ static int propagate_precision(struct bpf_verifier_env *env,
state_reg = state->regs;
for (i = 0; i < BPF_REG_FP; i++, state_reg++) {
if (state_reg->type != SCALAR_VALUE ||
- !state_reg->precise)
+ !state_reg->precise ||
+ !(state_reg->live & REG_LIVE_READ))
continue;
if (env->log.level & BPF_LOG_LEVEL2)
verbose(env, "frame %d: propagating r%d\n", i, fr);
@@ -10630,7 +10631,8 @@ static int propagate_precision(struct bpf_verifier_env *env,
continue;
state_reg = &state->stack[i].spilled_ptr;
if (state_reg->type != SCALAR_VALUE ||
- !state_reg->precise)
+ !state_reg->precise ||
+ !(state_reg->live & REG_LIVE_READ))
continue;
if (env->log.level & BPF_LOG_LEVEL2)
verbose(env, "frame %d: propagating fp%d\n",
