linux-kernel - [PATCH 1/1] pgo: Fix allocate_node() handling of non-vmlinux nodes.

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Date:   Wed,  2 Jun 2021 03:57:04 +0300
From:   Jarmo Tiitto <jarmo.tiitto@...il.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>,
        Bill Wendling <wcw@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com, linux-kernel@...r.kernel.org
Cc:     Jarmo Tiitto <jarmo.tiitto@...il.com>, morbo@...gle.com
Subject: [PATCH 1/1] pgo: Fix allocate_node() handling of non-vmlinux nodes.

Currently allocate_node() will reserve nodes even if *p
doesn't point into __llvm_prf_data_start - __llvm_prf_data_end
range.

Fix it by checking if p points into vmlinux range
and otherwise return NULL.

Signed-off-by: Jarmo Tiitto <jarmo.tiitto@...il.com>
---
 kernel/pgo/instrument.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/pgo/instrument.c b/kernel/pgo/instrument.c
index 0e07ee1b17d9..9bca535dfa91 100644
--- a/kernel/pgo/instrument.c
+++ b/kernel/pgo/instrument.c
@@ -55,6 +55,10 @@ void prf_unlock(unsigned long flags)
 static struct llvm_prf_value_node *allocate_node(struct llvm_prf_data *p,
 						 u32 index, u64 value)
 {
+	/* check if p points into vmlinux. If not, don't allocate. */
+	if (p < __llvm_prf_data_start || p >= __llvm_prf_data_end)
+		return NULL;
+
 	if (&__llvm_prf_vnds_start[current_node + 1] >= __llvm_prf_vnds_end)
 		return NULL; /* Out of nodes */
 
-- 
2.31.1