From: Francis Laniel <flaniel@linux.microsoft.com>
To: linux-kernel@vger.kernel.org
Cc: Alban Crequy <alban.crequy@gmail.com>,
Alban Crequy <albancrequy@microsoft.com>,
Francis Laniel <flaniel@linux.microsoft.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andrii Nakryiko <andrii@kernel.org>,
Mykola Lysenko <mykolal@fb.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>, Shuah Khan <shuah@kernel.org>,
linux-mm@kvack.org, bpf@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: [RFC PATCH v1 1/2] maccess: fix writing offset in case of fault in strncpy_from_kernel_nofault()
Date: Tue, 8 Nov 2022 20:52:06 +0100 [thread overview]
Message-ID: <20221108195211.214025-2-flaniel@linux.microsoft.com> (raw)
In-Reply-To: <20221108195211.214025-1-flaniel@linux.microsoft.com>
From: Alban Crequy <albancrequy@microsoft.com>
If a page fault occurs while copying the first byte, this function resets one
byte before dst.
As a consequence, an address could be modified and leaded to kernel crashes if
case the modified address was accessed later.
Signed-off-by: Alban Crequy <albancrequy@microsoft.com>
Tested-by: Francis Laniel <flaniel@linux.microsoft.com>
---
mm/maccess.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/maccess.c b/mm/maccess.c
index 5f4d240f67ec..074f6b086671 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -97,7 +97,7 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
return src - unsafe_addr;
Efault:
pagefault_enable();
- dst[-1] = '\0';
+ dst[0] = '\0';
return -EFAULT;
}
--
2.25.1
next prev parent reply other threads:[~2022-11-08 19:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-08 19:52 [RFC PATCH v1 0/2] Fix offset when fault occurs " Francis Laniel
2022-11-08 19:52 ` Francis Laniel [this message]
2022-11-08 20:35 ` [RFC PATCH v1 1/2] maccess: fix writing offset in case of fault " Yonghong Song
2022-11-08 20:38 ` Yonghong Song
2022-11-09 11:23 ` Alban Crequy
2022-11-09 16:09 ` Yonghong Song
2022-11-08 21:05 ` Andrew Morton
2022-11-08 19:52 ` [RFC PATCH v1 2/2] selftests: bpf: add a test when bpf_probe_read_kernel_str() returns EFAULT Francis Laniel
2022-11-08 22:06 ` Yonghong Song
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