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cifs: negotiate chained SMB2 compression capabilities

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Advertise LZ77 and Pattern_V1 with chained transform support in the
SMB 3.1.1 compression negotiate context. Validate the server's returned
algorithm list and flags, then retain the negotiated capabilities for a
future compressed transform receive implementation.

This patch only negotiates capabilities. It does not request compressed
READ responses or add a compressed transform receive path.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Namjae Jeon 2026-06-10 23:40:58 +09:00 committed by Steve French
parent 6234f50105
commit 17e12b1d14
2 changed files with 37 additions and 9 deletions
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2
fs/smb/client/cifsglob.h
View File

@ -789,6 +789,8 @@ struct TCP_Server_Info {
struct {
bool requested; /* "compress" mount option set*/
bool enabled; /* actually negotiated with server */
bool chained; /* chained transforms were negotiated */
bool pattern; /* Pattern_V1 chained payloads were negotiated */
__le16 alg; /* preferred alg negotiated with server */
} compression;
__u16 signing_algorithm;

44
fs/smb/client/smb2pdu.c
View File

@ -636,10 +636,16 @@ build_compression_ctxt(struct smb2_compression_capabilities_context *pneg_ctxt)
pneg_ctxt->DataLength =
cpu_to_le16(sizeof(struct smb2_compression_capabilities_context)
- sizeof(struct smb2_neg_context));
pneg_ctxt->CompressionAlgorithmCount = cpu_to_le16(3);
/*
* Pattern_V1 is useful only as part of a chained transform. LZ77 remains
* the preferred general-purpose algorithm selected by this client.
*/
pneg_ctxt->CompressionAlgorithmCount = cpu_to_le16(4);
pneg_ctxt->Flags = SMB2_COMPRESSION_CAPABILITIES_FLAG_CHAINED;
pneg_ctxt->CompressionAlgorithms[0] = SMB3_COMPRESS_LZ77;
pneg_ctxt->CompressionAlgorithms[1] = SMB3_COMPRESS_LZ77_HUFF;
pneg_ctxt->CompressionAlgorithms[2] = SMB3_COMPRESS_LZNT1;
pneg_ctxt->CompressionAlgorithms[3] = SMB3_COMPRESS_PATTERN;
}
static unsigned int
@ -827,9 +833,12 @@ static void decode_compress_ctx(struct TCP_Server_Info *server,
struct smb2_compression_capabilities_context *ctxt)
{
unsigned int len = le16_to_cpu(ctxt->DataLength);
__le16 alg;
unsigned int count, i;
server->compression.enabled = false;
server->compression.chained = false;
server->compression.pattern = false;
server->compression.alg = SMB3_COMPRESS_NONE;
/*
* Caller checked that DataLength remains within SMB boundary. We still
@ -841,20 +850,37 @@ static void decode_compress_ctx(struct TCP_Server_Info *server,
return;
}
if (le16_to_cpu(ctxt->CompressionAlgorithmCount) != 1) {
count = le16_to_cpu(ctxt->CompressionAlgorithmCount);
if (!count || count > ARRAY_SIZE(ctxt->CompressionAlgorithms) ||
len < 8 + count * sizeof(__le16)) {
pr_warn_once("invalid SMB3 compress algorithm count\n");
return;
}
alg = ctxt->CompressionAlgorithms[0];
/* 'NONE' (0) compressor type is never negotiated */
if (alg == 0 || le16_to_cpu(alg) > 3) {
pr_warn_once("invalid compression algorithm '%u'\n", alg);
if (ctxt->Flags != SMB2_COMPRESSION_CAPABILITIES_FLAG_NONE &&
ctxt->Flags != SMB2_COMPRESSION_CAPABILITIES_FLAG_CHAINED) {
pr_warn_once("invalid SMB3 compression flags\n");
return;
}
server->compression.alg = alg;
for (i = 0; i < count; i++) {
/* Record the intersection supported by the shared SMB codec. */
if (ctxt->CompressionAlgorithms[i] == SMB3_COMPRESS_LZ77)
server->compression.alg = SMB3_COMPRESS_LZ77;
else if (ctxt->CompressionAlgorithms[i] == SMB3_COMPRESS_PATTERN)
server->compression.pattern = true;
}
if (server->compression.alg != SMB3_COMPRESS_LZ77)
return;
/*
* Pattern_V1 cannot appear in an unchained transform even if a broken
* peer lists it in the algorithm array.
*/
server->compression.chained =
ctxt->Flags == SMB2_COMPRESSION_CAPABILITIES_FLAG_CHAINED;
if (!server->compression.chained)
server->compression.pattern = false;
server->compression.enabled = true;
}