diff options
Diffstat (limited to 'winsup/cygwin/fhandler/base.cc')
| -rw-r--r-- | winsup/cygwin/fhandler/base.cc | 48 |
1 files changed, 32 insertions, 16 deletions
diff --git a/winsup/cygwin/fhandler/base.cc b/winsup/cygwin/fhandler/base.cc index a5d15c7..32aca2c 100644 --- a/winsup/cygwin/fhandler/base.cc +++ b/winsup/cygwin/fhandler/base.cc @@ -526,8 +526,9 @@ fhandler_base::open (int flags, mode_t mode) ULONG file_attributes = 0; ULONG shared = (get_major () == DEV_TAPE_MAJOR ? 0 : FILE_SHARE_VALID_FLAGS); ULONG create_disposition; + FILE_BASIC_INFORMATION fbi; OBJECT_ATTRIBUTES attr; - IO_STATUS_BLOCK io; + IO_STATUS_BLOCK io, io_bi; NTSTATUS status; PFILE_FULL_EA_INFORMATION p = NULL; ULONG plen = 0; @@ -719,16 +720,32 @@ fhandler_base::open (int flags, mode_t mode) goto done; } - if (io.Information == FILE_CREATED) - { - /* Correct file attributes are needed for later use in, e.g. fchmod. */ - FILE_BASIC_INFORMATION fbi; + /* Fix up file attributes, they are desperately needed later. + + Originally we only did that in the FILE_CREATED case below, but that's + insufficient: - if (!NT_SUCCESS (NtQueryInformationFile (fh, &io, &fbi, sizeof fbi, - FileBasicInformation))) - fbi.FileAttributes = file_attributes | FILE_ATTRIBUTE_ARCHIVE; - pc.file_attributes (fbi.FileAttributes); + If two threads try to create the same file at the same time, it's + possible that path_conv::check returns the file as non-existant, i. e., + pc.file_attributes () returns INVALID_FILE_ATTRIBUTES, 0xffffffff. + However, one of the NtCreateFile will beat the other, so only one of + them returns with FILE_CREATED. + The other fhandler_base::open() will instead run into the O_TRUNC + conditional (further below), blindly check for the SPARSE attribute + and remove that bit. The result is that the attributes will be + 0xfffffdff, i.e., everything but SPARSE. Most annoying is that + pc.isdir() will return TRUE. Hilarity ensues. + + Note that we use a different IO_STATUS_BLOCK, so as not to overwrite + io.Information... */ + if (!NT_SUCCESS (NtQueryInformationFile (fh, &io_bi, &fbi, sizeof fbi, + FileBasicInformation))) + fbi.FileAttributes = file_attributes | FILE_ATTRIBUTE_ARCHIVE; + pc.file_attributes (fbi.FileAttributes); + + if (io.Information == FILE_CREATED) + { /* Always create files using a NULL SD. Create correct permission bits afterwards, maintaining the owner and group information just like chmod. This is done for two reasons. @@ -752,18 +769,17 @@ fhandler_base::open (int flags, mode_t mode) set_created_file_access (fh, pc, mode); } - /* If you O_TRUNC a file on Linux, the data is truncated, but the EAs are - preserved. If you open a file on Windows with FILE_OVERWRITE{_IF} or - FILE_SUPERSEDE, all streams are truncated, including the EAs. So we don't - use the FILE_OVERWRITE{_IF} flags, but instead just open the file and set - the size of the data stream explicitely to 0. Apart from being more Linux - compatible, this implementation has the pleasant side-effect to be more - than 5% faster than using FILE_OVERWRITE{_IF} (tested on W7 32 bit). */ if ((flags & O_TRUNC) && (flags & O_ACCMODE) != O_RDONLY && io.Information != FILE_CREATED && get_device () == FH_FS) { + /* If you O_TRUNC a file on Linux, the data is truncated, but the EAs are + preserved. If you open a file on Windows with FILE_OVERWRITE{_IF} or + FILE_SUPERSEDE, all streams are truncated, including the EAs. So we + don't use FILE_OVERWRITE{_IF} but just open the file and truncate the + data stream to size 0. Apart from being more Linux compatible, this + has the pleasant side-effect to be more than 5% faster. */ FILE_END_OF_FILE_INFORMATION feofi = { EndOfFile:{ QuadPart:0 } }; status = NtSetInformationFile (fh, &io, &feofi, sizeof feofi, FileEndOfFileInformation); |