[PATCH v3 1/2] ntdll: Allow renaming a file/directory to a different casing of itself.
Gabriel Ivăncescu
gabrielopcode at gmail.com
Tue Apr 20 07:33:08 CDT 2021
Hi Rémi,
Thanks for the review!
On 20/04/2021 10:27, Rémi Bernon wrote:
> Hi Gabriel,
>
> I don't know much about the code but I had a look nonetheless, hopefully
> it'll help.
>
> On 4/9/21 5:47 PM, Gabriel Ivăncescu wrote:
>> Renaming a file or directory from e.g. foobar to FooBar (or any other
>> casing
>> change) should work, like on Windows, instead of being a no-op.
>> Clobbering
>> an existing file must also respect the new casing.
>>
>> Note that we only send the different casing (and thus casing_len != 0) if
>> it's actually different. This is important to preserve atomicity of
>> rename()
>> in wineserver in all other cases that don't require this special casing
>> handling. The only extra time rename() is not atomic is when an existing
>> file is clobbered with a different casing, since we have to unlink the
>> old
>> file first, then rename the new file into the new casing, but there's no
>> way around that...
>>
>> Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=46203
>> Signed-off-by: Gabriel Ivăncescu <gabrielopcode at gmail.com>
>> ---
>>
>> We just prepend the unix casing filename (without path) to the wineserver
>> data before the actual unix filename, and add an extra (optional) field
>> `casing_len` which is the length of this data. If there's no casing, this
>> is zero and the behavior is identical to before, which is the default.
>>
>> dlls/ntdll/unix/file.c | 46 ++++++++++++++++++---
>> server/fd.c | 94 +++++++++++++++++++++++++++++-------------
>> server/protocol.def | 2 +
>> 3 files changed, 107 insertions(+), 35 deletions(-)
>>
>> diff --git a/dlls/ntdll/unix/file.c b/dlls/ntdll/unix/file.c
>> index 9ee5e84..fa604a1 100644
>> --- a/dlls/ntdll/unix/file.c
>> +++ b/dlls/ntdll/unix/file.c
>> @@ -4508,8 +4508,9 @@ NTSTATUS WINAPI NtSetInformationFile( HANDLE
>> handle, IO_STATUS_BLOCK *io,
>> {
>> FILE_RENAME_INFORMATION *info = ptr;
>> UNICODE_STRING name_str, nt_name = { 0 };
>> + char *unix_name, *casing = NULL;
>> OBJECT_ATTRIBUTES attr;
>> - char *unix_name;
>> + int casing_len = 0;
>> name_str.Buffer = info->FileName;
>> name_str.Length = info->FileNameLength;
>> @@ -4524,19 +4525,52 @@ NTSTATUS WINAPI NtSetInformationFile( HANDLE
>> handle, IO_STATUS_BLOCK *io,
>> if (io->u.Status != STATUS_SUCCESS && io->u.Status !=
>> STATUS_NO_SUCH_FILE)
>> break;
>> + /* get the casing of the last component if target exists */
>> + if (io->u.Status != STATUS_NO_SUCH_FILE)
>> + {
>> + const WCHAR *nt_filename = name_str.Buffer +
>> name_str.Length / sizeof(WCHAR);
>> + size_t nt_filename_len;
>> +
>> + /* name_str is not NUL terminated; look for last \
>> character */
>> + for (; nt_filename != name_str.Buffer; nt_filename--)
>> + if (nt_filename[-1] == '\\')
>> + break;
>> + nt_filename_len = name_str.Buffer + name_str.Length /
>> sizeof(WCHAR) - nt_filename;
>> +
>> + /* see if only casing differs from nt_name and update
>> it */
>> + if (nt_name.Length / sizeof(WCHAR) >= nt_filename_len)
>> + {
>> + WCHAR *p = nt_name.Buffer + nt_name.Length /
>> sizeof(WCHAR) - nt_filename_len;
>> +
>> + if ((p == nt_name.Buffer || p[-1] == '\\') &&
>> + memcmp( p, nt_filename, nt_filename_len *
>> sizeof(WCHAR) ) &&
>> + !wcsnicmp( p, nt_filename, nt_filename_len ) &&
>> + (casing = malloc( nt_filename_len * 3 )))
>> + {
>> + casing_len = ntdll_wcstoumbs( nt_filename,
>> nt_filename_len, casing,
>> + nt_filename_len
>> * 3, TRUE );
>> + if (casing_len < 0) casing_len = 0;
>> + if (casing_len) memcpy( p, nt_filename,
>> nt_filename_len * sizeof(WCHAR) );
>> + }
>> + }
>> + }
>
> This code recently changed upstream so it'll have to be rebased (the
> nt_name and name_str buffers are now the same so there's no need to
> update it anymore).
>
> Anyway, this feels a bit overcomplicated, and imho we could just always
> send the correct case version of the file name in addition to the
> matched unix file path.
>
> It would also need to be sent with the other set_fd_name_info below.
>
Ah ok, when I wrote this, I was worried that would make it less
upstreamable because it changed all the operation behavior, not just
when the casing is needed, which had more possible side-effects etc.
>> +
>> SERVER_START_REQ( set_fd_name_info )
>> {
>> - req->handle = wine_server_obj_handle( handle );
>> - req->rootdir = wine_server_obj_handle(
>> attr.RootDirectory );
>> - req->namelen = nt_name.Length;
>> - req->link = FALSE;
>> - req->replace = info->ReplaceIfExists;
>> + req->handle = wine_server_obj_handle( handle );
>> + req->rootdir = wine_server_obj_handle(
>> attr.RootDirectory );
>> + req->namelen = nt_name.Length;
>> + req->casing_len = casing_len;
>> + req->link = FALSE;
>> + req->replace = info->ReplaceIfExists;
>> wine_server_add_data( req, nt_name.Buffer,
>> nt_name.Length );
>> + wine_server_add_data( req, casing, casing_len );
>> wine_server_add_data( req, unix_name,
>> strlen(unix_name) );
>> io->u.Status = wine_server_call( req );
>> }
>> SERVER_END_REQ;
>> + free( casing );
>> free( unix_name );
>> free( nt_name.Buffer );
>> }
>> diff --git a/server/fd.c b/server/fd.c
>> index 481e9a8..502d958 100644
>> --- a/server/fd.c
>> +++ b/server/fd.c
>> @@ -2488,7 +2488,8 @@ static void set_fd_disposition( struct fd *fd,
>> int unlink )
>> /* set new name for the fd */
>> static void set_fd_name( struct fd *fd, struct fd *root, const char
>> *nameptr, data_size_t len,
>> - struct unicode_str nt_name, int create_link,
>> int replace )
>> + const char *casing, data_size_t casing_len,
>> struct unicode_str nt_name,
>> + int create_link, int replace )
>> {
>> struct inode *inode;
>> struct stat st, st2;
>> @@ -2538,45 +2539,77 @@ static void set_fd_name( struct fd *fd, struct
>> fd *root, const char *nameptr, da
>> if (!fstat( fd->unix_fd, &st2 ) && st.st_ino == st2.st_ino
>> && st.st_dev == st2.st_dev)
>> {
>> if (create_link && !replace) set_error(
>> STATUS_OBJECT_NAME_COLLISION );
>> - free( name );
>> - return;
>> - }
>> -
>> - if (!replace)
>> - {
>> - set_error( STATUS_OBJECT_NAME_COLLISION );
>> - goto failed;
>> + if (!casing_len)
>> + {
>> + free( name );
>> + return;
>> + }
>> }
>> -
>> - /* can't replace directories or special files */
>> - if (!S_ISREG( st.st_mode ))
>> + else
>> {
>> - set_error( STATUS_ACCESS_DENIED );
>> - goto failed;
>> - }
>> + if (!replace)
>> + {
>> + set_error( STATUS_OBJECT_NAME_COLLISION );
>> + goto failed;
>> + }
>> - /* can't replace an opened file */
>> - if ((inode = get_inode( st.st_dev, st.st_ino, -1 )))
>> - {
>> - int is_empty = list_empty( &inode->open );
>> - release_object( inode );
>> - if (!is_empty)
>> + /* can't replace directories or special files */
>> + if (!S_ISREG( st.st_mode ))
>> {
>> set_error( STATUS_ACCESS_DENIED );
>> goto failed;
>> }
>> +
>> + /* can't replace an opened file */
>> + if ((inode = get_inode( st.st_dev, st.st_ino, -1 )))
>> + {
>> + int is_empty = list_empty( &inode->open );
>> + release_object( inode );
>> + if (!is_empty)
>> + {
>> + set_error( STATUS_ACCESS_DENIED );
>> + goto failed;
>> + }
>> + }
>> +
>> + /* link() expects that the target doesn't exist */
>> + /* rename() cannot replace files with directories */
>> + /* we also have to unlink it if target has different
>> casing */
>> + if (create_link || S_ISDIR( st2.st_mode ) || casing_len)
>> + {
>> + if (unlink( name ))
>> + {
>> + file_set_error();
>> + goto failed;
>> + }
>> + }
>> }
>> + }
>
> Then I think this would also become simpler, with this first part being
> done on "name" (which is the unix path of a matching file), with a few
> more conditions to not return an error if "name" was the old name of the
> file and it's renamed to a different casing.
>
The problem here is that I'll have to check if the casing is the same or
not, so it would move that check from ntdll to the wineserver.
We have to check it for two reasons:
1) renaming a file into a different casing of itself
2) unlinking a target file first, if the casing is different
For (2), we currently use an atomic rename() so I'd like to keep it that
way unless absolutely needed (only in the case we clobber existing file
with different casing).
>> +
>> + /* replace the last component with its actual casing */
>> + if (casing_len)
>> + {
>> + char *p = strrchr( name, '/' );
>> + size_t orig_len, path_len;
>> +
>> + p = p ? p + 1 : name;
>> + path_len = p - name;
>> + orig_len = strlen(p);
>> - /* link() expects that the target doesn't exist */
>> - /* rename() cannot replace files with directories */
>> - if (create_link || S_ISDIR( st2.st_mode ))
>> + if (orig_len < casing_len)
>> {
>> - if (unlink( name ))
>> + char *new_name = mem_alloc( path_len + casing_len + 1 );
>> + if (!new_name)
>> {
>> - file_set_error();
>> + set_error( STATUS_NO_MEMORY );
>> goto failed;
>> }
>> + memcpy( new_name, name, path_len );
>> + free( name );
>> + name = new_name;
>> }
>> + memcpy(name + path_len, casing, casing_len);
>> + name[path_len + casing_len] = 0;
>> }
>
> Then, this instead could be simplified by replacing, unconditionally,
> the last element in the name path by the correctly cased version
> (possibly identical), before doing the link and rename calls.
>
I think, since I'm going to have to check if the casing is the same
anyway, that I should only copy the new casing if it's actually
different, to avoid the common case where it's not.
Note that this code won't really be simplified by doing it
unconditionally (that's just an if). What might simplify it, though, is
to allocate enough space to hold the new casing (if it's larger) at the
beginning so we don't have to reallocate.
I'll see if I can do that without introducing too much complexity, since
I have to scan the filename already now to see if the casing is different.
>> if (create_link)
>> @@ -2879,16 +2912,19 @@ DECL_HANDLER(set_fd_disp_info)
>> /* set fd name information */
>> DECL_HANDLER(set_fd_name_info)
>> {
>> + const char *filename, *casing;
>> struct fd *fd, *root_fd = NULL;
>> struct unicode_str nt_name;
>> - if (req->namelen > get_req_data_size())
>> + if (req->namelen > get_req_data_size() || get_req_data_size() -
>> req->namelen < req->casing_len)
>> {
>> set_error( STATUS_INVALID_PARAMETER );
>> return;
>> }
>> nt_name.str = get_req_data();
>> nt_name.len = (req->namelen / sizeof(WCHAR)) * sizeof(WCHAR);
>> + casing = (const char *)get_req_data() + req->namelen;
>> + filename = casing + req->casing_len;
>> if (req->rootdir)
>> {
>> @@ -2902,8 +2938,8 @@ DECL_HANDLER(set_fd_name_info)
>> if ((fd = get_handle_fd_obj( current->process, req->handle, 0 )))
>> {
>> - set_fd_name( fd, root_fd, (const char *)get_req_data() +
>> req->namelen,
>> - get_req_data_size() - req->namelen, nt_name,
>> req->link, req->replace );
>> + set_fd_name( fd, root_fd, filename, (const char
>> *)get_req_data() + get_req_data_size() - filename,
>> + casing, req->casing_len, nt_name, req->link,
>> req->replace );
>> release_object( fd );
>> }
>> if (root_fd) release_object( root_fd );
>> diff --git a/server/protocol.def b/server/protocol.def
>> index 617818f..d97cd1a 100644
>> --- a/server/protocol.def
>> +++ b/server/protocol.def
>> @@ -3532,9 +3532,11 @@ struct handle_info
>> obj_handle_t handle; /* handle to a file or directory */
>> obj_handle_t rootdir; /* root directory */
>> data_size_t namelen; /* length of NT name in bytes */
>> + data_size_t casing_len; /* length of the casing filename */
>> int link; /* link instead of renaming */
>> int replace; /* replace an existing file? */
>> VARARG(name,unicode_str,namelen); /* NT name */
>> + VARARG(casing,string,casing_len); /* new file name's actual
>> casing (without path) */
>> VARARG(filename,string); /* new file name */
>> @END
>>
>
> Cheers,
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