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Message-Id: <C22D945F-4C40-4C0E-8074-07747C944C99@linux.dev>
Date: Tue, 24 Sep 2024 21:33:15 +0200
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Tom Talpey <tom@...pey.com>
Cc: Namjae Jeon <linkinjeon@...nel.org>,
Steve French <sfrench@...ba.org>,
Sergey Senozhatsky <senozhatsky@...omium.org>,
Kees Cook <kees@...nel.org>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
linux-cifs@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-hardening@...r.kernel.org
Subject: Re: [PATCH] ksmbd: Annotate struct copychunk_ioctl_req with
__counted_by_le()
Hi Tom,
> On 24. Sep 2024, at 20:05, Tom Talpey <tom@...pey.com> wrote:
> On 9/24/2024 6:22 AM, Thorsten Blum wrote:
>> Add the __counted_by_le compiler attribute to the flexible array member
>> Chunks to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
>> CONFIG_FORTIFY_SOURCE.
>> Read Chunks[0] after checking that ChunkCount is not 0.
>> Compile-tested only.
>> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
>> ---
>> fs/smb/server/smb2pdu.c | 2 +-
>> fs/smb/server/smb2pdu.h | 2 +-
>> 2 files changed, 2 insertions(+), 2 deletions(-)
>> diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
>> index 461c4fc682ac..0670bdf3e167 100644
>> --- a/fs/smb/server/smb2pdu.c
>> +++ b/fs/smb/server/smb2pdu.c
>> @@ -7565,7 +7565,6 @@ static int fsctl_copychunk(struct ksmbd_work *work,
>> ci_rsp->TotalBytesWritten =
>> cpu_to_le32(ksmbd_server_side_copy_max_total_size());
>> - chunks = (struct srv_copychunk *)&ci_req->Chunks[0];
>> chunk_count = le32_to_cpu(ci_req->ChunkCount);
>> if (chunk_count == 0)
>> goto out;
>> @@ -7579,6 +7578,7 @@ static int fsctl_copychunk(struct ksmbd_work *work,
>> return -EINVAL;
>> }
>> + chunks = (struct srv_copychunk *)&ci_req->Chunks[0];
>> for (i = 0; i < chunk_count; i++) {
>> if (le32_to_cpu(chunks[i].Length) == 0 ||
>> le32_to_cpu(chunks[i].Length) > ksmbd_server_side_copy_max_chunk_size())
>> diff --git a/fs/smb/server/smb2pdu.h b/fs/smb/server/smb2pdu.h
>> index 73aff20e22d0..f01121dbf358 100644
>> --- a/fs/smb/server/smb2pdu.h
>> +++ b/fs/smb/server/smb2pdu.h
>> @@ -194,7 +194,7 @@ struct copychunk_ioctl_req {
>> __le64 ResumeKey[3];
>> __le32 ChunkCount;
>> __le32 Reserved;
>> - __u8 Chunks[]; /* array of srv_copychunk */
>> + __u8 Chunks[] __counted_by_le(ChunkCount); /* array of srv_copychunk */
>> } __packed;
>>
>
> This isn't correct. The u8 is just a raw buffer, copychunk structs are
> marshaled into it, and they're 24 bytes each.
Hm, I see.
How does this for-loop work then? It iterates over ci_req->ChunkCount
and expects a srv_copychunk at each ci_req->Chunks[i]?
for (i = 0; i < chunk_count; i++) {
if (le32_to_cpu(chunks[i].Length) == 0 ||
le32_to_cpu(chunks[i].Length) > ksmbd_server_side_copy_max_chunk_size())
break;
total_size_written += le32_to_cpu(chunks[i].Length);
}
Thanks,
Thorsten
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