Forwarded: [PATCH] bpf: Fix double offset in insn_array_map_direct_value_addr()

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Subject: [PATCH] bpf: Fix double offset in insn_array_map_direct_value_addr()
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git master

insn_array_map_direct_value_addr() adds the offset to the returned
address, but callers of map_direct_value_addr() expect the base address
and add the offset themselves. This is inconsistent with other
implementations like array_map_direct_value_addr() and
arena_map_direct_value_addr() which return only the base address.

This causes a double offset when check_reg_const_str() validates
ARG_PTR_TO_CONST_STR arguments, leading to an out-of-bounds read
in strnchr() when bpf_snprintf() is called with a format string
from an insn_array map.

Remove the offset addition to match the expected behavior.

Reported-by: syzbot+2c29addf92581b410079@syzkaller.appspotmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 kernel/bpf/bpf_insn_array.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/bpf_insn_array.c b/kernel/bpf/bpf_insn_array.c
index c96630cb75bf..37b43102953e 100644
--- a/kernel/bpf/bpf_insn_array.c
+++ b/kernel/bpf/bpf_insn_array.c
@@ -126,7 +126,7 @@ static int insn_array_map_direct_value_addr(const struct bpf_map *map, u64 *imm,
 		return -EINVAL;
 
 	/* from BPF's point of view, this map is a jump table */
-	*imm = (unsigned long)insn_array->ips + off;
+	*imm = (unsigned long)insn_array->ips;
 
 	return 0;
 }
-- 
2.43.0