6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Breno Leitao <leitao@debian.org>
[ Upstream commit 99985bfa8336fadcc69190ba2dcbd5386af3d661 ]
nfc_llcp_getsockopt() casts optval to (u32 __user *) for put_user(), so
the kernel always stores 4 bytes regardless of the caller-supplied
optlen. The existing min_t(u32, len, sizeof(u32)) only clamps the length
reported back to userspace; it does not constrain the store. A call with
optlen < 4 therefore writes past the user buffer, violating the
getsockopt(2) contract for all five supported optnames.
Reject any call with optlen < sizeof(u32) up front. 'len' is int, so a
plain size comparison would promote a negative optlen to size_t and slip
past the check; an explicit 'len < 0' test is added first to catch
negative values before the size compare.
Fixes: 26fd76cab2e6 ("NFC: llcp: Implement socket options")
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260521-fix_llc-v2-1-ab44cc09179c@debian.org (local)
Signed-off-by: David Heidelberg <david@ixit.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/nfc/llcp_sock.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c
index 6cdcc49a58bcd..a2c3d876c7d85 100644
--- a/net/nfc/llcp_sock.c
+++ b/net/nfc/llcp_sock.c
@@ -319,6 +319,12 @@ static int nfc_llcp_getsockopt(struct socket *sock, int level, int optname,
if (get_user(len, optlen))
return -EFAULT;
+ if (len < 0)
+ return -EINVAL;
+
+ if (len < sizeof(u32))
+ return -EINVAL;
+
local = llcp_sock->local;
if (!local)
return -ENODEV;
--
2.53.0