diff options
Diffstat (limited to 'winsup')
| -rw-r--r-- | winsup/cygwin/forkable.cc | 72 |
1 files changed, 48 insertions, 24 deletions
diff --git a/winsup/cygwin/forkable.cc b/winsup/cygwin/forkable.cc index 1e02a8a..1067eac 100644 --- a/winsup/cygwin/forkable.cc +++ b/winsup/cygwin/forkable.cc @@ -423,7 +423,14 @@ dll::nominate_forkable (PCWCHAR dirx_name) } /* Create the nominated hardlink for one indivitual dll, - inside another subdirectory when dynamically loaded. */ + inside another subdirectory when dynamically loaded. + + We've not found a performant way yet to protect fork against + updates to main executables and/or dlls that do not reside on + the same NTFS filesystem as the <cygroot>/var/run/cygfork/ + directory. But as long as the main executable can be hardlinked, + dll redirection works for any other hardlink-able dll, while + non-hardlink-able dlls are used from their original location. */ bool dll::create_forkable () { @@ -465,14 +472,6 @@ dll::create_forkable () if (devhandle == INVALID_HANDLE_VALUE) return false; /* impossible */ - HANDLE fh = dll_list::ntopenfile ((PCWCHAR)&fii.IndexNumber, NULL, - FILE_OPEN_BY_FILE_ID, - FILE_WRITE_ATTRIBUTES, - devhandle); - NtClose (devhandle); - if (fh == INVALID_HANDLE_VALUE) - return false; /* impossible */ - int ntlen = wcslen (ntname); int bufsize = sizeof (FILE_LINK_INFORMATION) + ntlen * sizeof (*ntname); PFILE_LINK_INFORMATION pfli = (PFILE_LINK_INFORMATION) alloca (bufsize); @@ -483,22 +482,47 @@ dll::create_forkable () pfli->ReplaceIfExists = FALSE; /* allow concurrency */ pfli->RootDirectory = NULL; - IO_STATUS_BLOCK iosb; - NTSTATUS status = NtSetInformationFile (fh, &iosb, pfli, bufsize, - FileLinkInformation); - NtClose (fh); - debug_printf ("%y = NtSetInformationFile (%p, FileLink %W, iosb.Status %y)", - status, fh, pfli->FileName, iosb.Status); - if (NT_SUCCESS (status) || status == STATUS_OBJECT_NAME_COLLISION) - /* We've not found a performant way yet to protect fork against updates - to main executables and/or dlls that do not reside on the same NTFS - filesystem as the <cygroot>/var/run/cygfork/ directory. - But as long as the main executable can be hardlinked, dll redirection - works for any other hardlink-able dll, while non-hardlink-able dlls - are used from their original location. */ - return true; + /* When we get STATUS_TRANSACTION_NOT_ACTIVE from hardlink creation, + the current process has renamed the file while it had the readonly + attribute. The rename() function uses a transaction for combined + writeable+rename action if possible to provide atomicity. + Although the transaction is closed afterwards, creating a hardlink + for this file requires the FILE_WRITE_ATTRIBUTES access, for unknown + reason. On the other hand, always requesting FILE_WRITE_ATTRIBUTES + would fail for users that do not own the original file. */ + bool ret = false; + int access = 0; /* first attempt */ + while (true) + { + HANDLE fh = dll_list::ntopenfile ((PCWCHAR)&fii.IndexNumber, NULL, + FILE_OPEN_BY_FILE_ID, + access, + devhandle); + if (fh == INVALID_HANDLE_VALUE) + break; /* impossible */ + + IO_STATUS_BLOCK iosb; + NTSTATUS status = NtSetInformationFile (fh, &iosb, pfli, bufsize, + FileLinkInformation); + NtClose (fh); + debug_printf ("%y = NtSetInformationFile (%p, FileLink %W, iosb.Status %y)", + status, fh, pfli->FileName, iosb.Status); + if (NT_SUCCESS (status) || status == STATUS_OBJECT_NAME_COLLISION) + { + ret = true; + break; + } + + if (status != STATUS_TRANSACTION_NOT_ACTIVE || + access == FILE_WRITE_ATTRIBUTES) + break; + + access = FILE_WRITE_ATTRIBUTES; /* second attempt */ + } + + NtClose (devhandle); - return false; + return ret; } /* return the number of characters necessary to store one forkable name */ |