* [bug report] smb: client: batch SRV_COPYCHUNK entries to cut roundtrips
@ 2025-09-18 9:44 Dan Carpenter
2025-09-18 20:19 ` Henrique Carvalho
0 siblings, 1 reply; 3+ messages in thread
From: Dan Carpenter @ 2025-09-18 9:44 UTC (permalink / raw)
To: Henrique Carvalho; +Cc: linux-cifs
Hello Henrique Carvalho,
Commit 4e3acdf94c89 ("smb: client: batch SRV_COPYCHUNK entries to cut
roundtrips") from Sep 16, 2025 (linux-next), leads to the following
Smatch static checker warning:
fs/smb/client/smb2ops.c:1937 smb2_copychunk_range()
error: uninitialized symbol 'ret_data_len'.
fs/smb/client/smb2ops.c
1844 static ssize_t
1845 smb2_copychunk_range(const unsigned int xid,
1846 struct cifsFileInfo *src_file,
1847 struct cifsFileInfo *dst_file,
1848 u64 src_off,
1849 u64 len,
1850 u64 dst_off)
1851 {
1852 int rc = 0;
1853 unsigned int ret_data_len;
1854 struct copychunk_ioctl *cc_req = NULL;
1855 struct copychunk_ioctl_rsp *cc_rsp = NULL;
1856 struct cifs_tcon *tcon;
1857 struct copychunk *chunk;
1858 u32 chunks, chunk_count, chunk_bytes;
1859 u32 copy_bytes, copy_bytes_left;
1860 u32 chunks_written, bytes_written;
1861 u64 total_bytes_left = len;
1862 u64 src_off_prev, dst_off_prev;
1863 u32 retries = 0;
1864
1865 tcon = tlink_tcon(dst_file->tlink);
1866
1867 trace_smb3_copychunk_enter(xid, src_file->fid.volatile_fid,
1868 dst_file->fid.volatile_fid, tcon->tid,
1869 tcon->ses->Suid, src_off, dst_off, len);
1870
1871 retry:
1872 chunk_count = calc_chunk_count(tcon, total_bytes_left);
1873 if (!chunk_count) {
1874 rc = -EOPNOTSUPP;
1875 goto cchunk_out;
1876 }
1877
1878 cc_req = kzalloc(struct_size(cc_req, Chunks, chunk_count), GFP_KERNEL);
1879 if (!cc_req) {
1880 rc = -ENOMEM;
1881 goto cchunk_out;
1882 }
1883
1884 /* Request a key from the server to identify the source of the copy */
1885 rc = SMB2_request_res_key(xid,
1886 tlink_tcon(src_file->tlink),
1887 src_file->fid.persistent_fid,
1888 src_file->fid.volatile_fid,
1889 cc_req);
1890
1891 /* Note: request_res_key sets res_key null only if rc != 0 */
1892 if (rc)
1893 goto cchunk_out;
1894
1895 while (total_bytes_left > 0) {
1896
1897 /* Store previous offsets to allow rewind */
1898 src_off_prev = src_off;
1899 dst_off_prev = dst_off;
1900
1901 trace_smb3_copychunk_iter(xid, src_file->fid.volatile_fid,
1902 dst_file->fid.volatile_fid, tcon->tid,
1903 tcon->ses->Suid, src_off, dst_off, len);
1904
1905 chunks = 0;
1906 copy_bytes = 0;
1907 copy_bytes_left = umin(total_bytes_left, tcon->max_bytes_copy);
1908 while (copy_bytes_left > 0 && chunks < chunk_count) {
1909 chunk = &cc_req->Chunks[chunks++];
1910
1911 chunk->SourceOffset = cpu_to_le64(src_off);
1912 chunk->TargetOffset = cpu_to_le64(dst_off);
1913
1914 chunk_bytes = umin(copy_bytes_left, tcon->max_bytes_chunk);
1915
1916 chunk->Length = cpu_to_le32(chunk_bytes);
1917 chunk->Reserved = 0;
1918
1919 src_off += chunk_bytes;
1920 dst_off += chunk_bytes;
1921
1922 copy_bytes_left -= chunk_bytes;
1923 copy_bytes += chunk_bytes;
1924 }
1925
1926 cc_req->ChunkCount = cpu_to_le32(chunks);
1927 /* Buffer is zeroed, no need to set pcchunk->Reserved = 0 */
1928
1929 /* Request server copy to target from src identified by key */
1930 kfree(cc_rsp);
1931 cc_rsp = NULL;
1932 rc = SMB2_ioctl(xid, tcon, dst_file->fid.persistent_fid,
1933 dst_file->fid.volatile_fid, FSCTL_SRV_COPYCHUNK_WRITE,
1934 (char *)cc_req, struct_size(cc_req, Chunks, chunks),
1935 CIFSMaxBufSize, (char **)&cc_rsp, &ret_data_len);
1936
--> 1937 if (ret_data_len != sizeof(struct copychunk_ioctl_rsp)) {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Using unintialized variables doesn't work because runtime checkers like
UBSan will complain as well as static checkers.
But the other issue is that this code treats -EINVAL as having a special
meaning. -EINVAL is the most common error code. All the places which
treat -EINVAL as having a special meaning end up buggy in the end. Mostly
they start out buggy, but even the ones which aren't buggy from the start
end up buggy over time.
1938 cifs_tcon_dbg(VFS, "Copychunk invalid response: response size does not match expected size\n");
1939 rc = -EIO;
1940 goto cchunk_out;
1941 }
1942
1943 if (rc == 0) {
1944 bytes_written = le32_to_cpu(cc_rsp->TotalBytesWritten);
1945 if (bytes_written == 0) {
1946 cifs_tcon_dbg(VFS, "Copychunk invalid response: no bytes copied\n");
1947 rc = -EIO;
1948 goto cchunk_out;
1949 }
1950 /* Check if server claimed to write more than we asked */
1951 if (bytes_written > copy_bytes) {
1952 cifs_tcon_dbg(VFS, "Copychunk invalid response: unexpected value for TotalBytesWritten\n");
1953 rc = -EIO;
1954 goto cchunk_out;
1955 }
1956
1957 chunks_written = le32_to_cpu(cc_rsp->ChunksWritten);
1958 if (chunks_written > chunks) {
1959 cifs_tcon_dbg(VFS, "Copychunk invalid response: Invalid num chunks written\n");
1960 rc = -EIO;
1961 goto cchunk_out;
1962 }
1963
1964 /* Partial write: rewind */
1965 if (bytes_written < copy_bytes) {
1966 u32 delta = copy_bytes - bytes_written;
1967
1968 src_off -= delta;
1969 dst_off -= delta;
1970 }
1971
1972 total_bytes_left -= bytes_written;
1973
1974 } else if (rc == -EINVAL) {
1975 /*
1976 * Check if server is not asking us to reduce size.
1977 *
1978 * Note: As per MS-SMB2 2.2.32.1, the values returned
1979 * in cc_rsp are not strictly lower than what existed
1980 * before.
1981 *
1982 */
1983 if (le32_to_cpu(cc_rsp->ChunksWritten) < tcon->max_chunks) {
1984 cifs_tcon_dbg(VFS, "Copychunk MaxChunks updated: %u -> %u\n",
1985 tcon->max_chunks,
1986 le32_to_cpu(cc_rsp->ChunksWritten));
1987 tcon->max_chunks = le32_to_cpu(cc_rsp->ChunksWritten);
1988 }
1989 if (le32_to_cpu(cc_rsp->ChunkBytesWritten) < tcon->max_bytes_chunk) {
1990 cifs_tcon_dbg(VFS, "Copychunk MaxBytesChunk updated: %u -> %u\n",
1991 tcon->max_bytes_chunk,
1992 le32_to_cpu(cc_rsp->ChunkBytesWritten));
1993 tcon->max_bytes_chunk = le32_to_cpu(cc_rsp->ChunkBytesWritten);
1994 }
1995 if (le32_to_cpu(cc_rsp->TotalBytesWritten) < tcon->max_bytes_copy) {
1996 cifs_tcon_dbg(VFS, "Copychunk MaxBytesCopy updated: %u -> %u\n",
1997 tcon->max_bytes_copy,
1998 le32_to_cpu(cc_rsp->TotalBytesWritten));
1999 tcon->max_bytes_copy = le32_to_cpu(cc_rsp->TotalBytesWritten);
2000 }
2001
2002 trace_smb3_copychunk_err(xid, src_file->fid.volatile_fid,
2003 dst_file->fid.volatile_fid, tcon->tid,
2004 tcon->ses->Suid, src_off, dst_off, len, rc);
2005
2006 /* Rewind */
2007 if (retries++ < 2) {
2008 src_off = src_off_prev;
2009 dst_off = dst_off_prev;
2010 kfree(cc_req);
2011 cc_req = NULL;
2012 goto retry;
2013 } else
2014 goto cchunk_out;
2015 } else { /* Unexpected */
2016 trace_smb3_copychunk_err(xid, src_file->fid.volatile_fid,
2017 dst_file->fid.volatile_fid, tcon->tid,
2018 tcon->ses->Suid, src_off, dst_off, len, rc);
2019 goto cchunk_out;
2020 }
2021 }
2022
2023 trace_smb3_copychunk_done(xid, src_file->fid.volatile_fid,
2024 dst_file->fid.volatile_fid, tcon->tid,
2025 tcon->ses->Suid, src_off, dst_off, len);
2026
2027 cchunk_out:
2028 kfree(cc_req);
2029 kfree(cc_rsp);
2030 if (rc)
2031 return rc;
2032 else
2033 return len;
2034 }
regards,
dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [bug report] smb: client: batch SRV_COPYCHUNK entries to cut roundtrips
2025-09-18 9:44 [bug report] smb: client: batch SRV_COPYCHUNK entries to cut roundtrips Dan Carpenter
@ 2025-09-18 20:19 ` Henrique Carvalho
2025-09-18 20:59 ` Henrique Carvalho
0 siblings, 1 reply; 3+ messages in thread
From: Henrique Carvalho @ 2025-09-18 20:19 UTC (permalink / raw)
To: Dan Carpenter; +Cc: linux-cifs
Hi Dan,
Thanks for the report.
On 9/18/25 6:44 AM, Dan Carpenter wrote:
> Hello Henrique Carvalho,
>
> Commit 4e3acdf94c89 ("smb: client: batch SRV_COPYCHUNK entries to cut
> roundtrips") from Sep 16, 2025 (linux-next), leads to the following
> Smatch static checker warning:
>
> fs/smb/client/smb2ops.c:1937 smb2_copychunk_range()
> error: uninitialized symbol 'ret_data_len'.
>
> --> 1937 if (ret_data_len != sizeof(struct copychunk_ioctl_rsp)) {
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Using unintialized variables doesn't work because runtime checkers like
> UBSan will complain as well as static checkers.
I will update the patch to initialize ret_data_len.
> But the other issue is that this code treats -EINVAL as having a special
> meaning. -EINVAL is the most common error code. All the places which
> treat -EINVAL as having a special meaning end up buggy in the end. Mostly
> they start out buggy, but even the ones which aren't buggy from the start
> end up buggy over time.
-EINVAL is mapped from the SMB2 server returned error
STATUS_INVALID_PARAMETER, so I don't know if there is anything that can
be done here.
After your email, I considered returning -EOPNOTSUPP instead to trigger
kernel-side copy fallback, but returning -EINVAL also seems to have the
practical advantage of having a successful copy, but with fewer network
roundtrips (apparently due to userspace fallback, but I haven't digged
too much into it).
If there's consensus that changing this error mapping would improve the
overall robustness of the code path, I'm open to that approach.
--
Henrique
SUSE Labs
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [bug report] smb: client: batch SRV_COPYCHUNK entries to cut roundtrips
2025-09-18 20:19 ` Henrique Carvalho
@ 2025-09-18 20:59 ` Henrique Carvalho
0 siblings, 0 replies; 3+ messages in thread
From: Henrique Carvalho @ 2025-09-18 20:59 UTC (permalink / raw)
To: Dan Carpenter; +Cc: linux-cifs
On 9/18/25 5:19 PM, Henrique Carvalho wrote:
> Hi Dan,
>
> Thanks for the report.
>
> On 9/18/25 6:44 AM, Dan Carpenter wrote:
>> Hello Henrique Carvalho,
>>
>> Commit 4e3acdf94c89 ("smb: client: batch SRV_COPYCHUNK entries to cut
>> roundtrips") from Sep 16, 2025 (linux-next), leads to the following
>> Smatch static checker warning:
>>
>> fs/smb/client/smb2ops.c:1937 smb2_copychunk_range()
>> error: uninitialized symbol 'ret_data_len'.
>>
>> --> 1937 if (ret_data_len != sizeof(struct copychunk_ioctl_rsp)) {
>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> Using unintialized variables doesn't work because runtime checkers like
>> UBSan will complain as well as static checkers.
>
> I will update the patch to initialize ret_data_len.
>
>> But the other issue is that this code treats -EINVAL as having a special
>> meaning. -EINVAL is the most common error code. All the places which
>> treat -EINVAL as having a special meaning end up buggy in the end. Mostly
>> they start out buggy, but even the ones which aren't buggy from the start
>> end up buggy over time.
>
> -EINVAL is mapped from the SMB2 server returned error
> STATUS_INVALID_PARAMETER, so I don't know if there is anything that can
> be done here.
>
> After your email, I considered returning -EOPNOTSUPP instead to trigger
> kernel-side copy fallback, but returning -EINVAL also seems to have the
> practical advantage of having a successful copy, but with fewer network
> roundtrips (apparently due to userspace fallback, but I haven't digged
> too much into it).
Correction: -EOPNOTSUPP seems to result in fewer network roundtrips for
big files. If anyone thinks this is worth digging more into, please let
me know.
But returning either errno will *not* result in an error to userpace in
case of cp.
>
> If there's consensus that changing this error mapping would improve the
> overall robustness of the code path, I'm open to that approach.
>
--
Henrique
SUSE Labs
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2025-09-18 21:02 UTC | newest]
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2025-09-18 9:44 [bug report] smb: client: batch SRV_COPYCHUNK entries to cut roundtrips Dan Carpenter
2025-09-18 20:19 ` Henrique Carvalho
2025-09-18 20:59 ` Henrique Carvalho
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