netdev - [PATCH 3/3] bpf: use copy_struct_from

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20191009160907.10981-4-christian.brauner@ubuntu.com>
Date:   Wed,  9 Oct 2019 18:09:07 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, bpf@...r.kernel.org
Cc:     Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>,
        Yonghong Song <yhs@...com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Christian Brauner <christian.brauner@...ntu.com>
Subject: [PATCH 3/3] bpf: use copy_struct_from_user() in bpf() syscall

In v5.4-rc2 we added a new helper (cf. [1]) copy_struct_from_user().
This helper is intended for all codepaths that copy structs from
userspace that are versioned by size. The bpf() syscall does exactly
what copy_struct_from_user() is doing.
Note that copy_struct_from_user() is calling min() already. So
technically, the min_t() call could go. But the size is used further
below so leave it.

[1]: f5a1a536fa14 ("lib: introduce copy_struct_from_user() helper")
Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
---
 kernel/bpf/syscall.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6f4f9097b1fe..6fdcbdb27501 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2819,14 +2819,11 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
 	if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	err = bpf_check_uarg_tail_zero(uattr, sizeof(attr), size);
-	if (err)
-		return err;
 	size = min_t(u32, size, sizeof(attr));
-
 	/* copy attributes from user space, may be less than sizeof(bpf_attr) */
-	if (copy_from_user(&attr, uattr, size) != 0)
-		return -EFAULT;
+	err = copy_struct_from_user(&attr, sizeof(attr), uattr, size);
+	if (err)
+		return err;
 
 	err = security_bpf(cmd, &attr, size);
 	if (err < 0)
-- 
2.23.0