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syscall: fix opening of directories on wasip1

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Go programs targeting GOOS=wasip1 were failing to open directories when
executed with runtimes like wasmtime or wasmedge due to requesting
rights for operations that are not supported on directories such as
fd_read, fd_write, etc...

This change addresses the issue by performing a second path_open when
observing EISDIR, and masking the requested rights to only ask for
permissions to perform operations supported by a directory.

Change-Id: Ibf65acf4a38bc848a649f41dbd026507d8b63c82
Reviewed-on: https://go-review.googlesource.com/c/go/+/490755
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Achille Roussel 2023-04-29 11:17:25 -07:00 committed by Gopher Robot
parent 4badad8d47
commit 4b66502dda
1 changed files with 83 additions and 4 deletions
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87
src/syscall/fs_wasip1.go
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@ -100,6 +100,63 @@ const (
fullRights = rights(^uint32(0))
readRights = rights(RIGHT_FD_READ | RIGHT_FD_READDIR)
writeRights = rights(RIGHT_FD_DATASYNC | RIGHT_FD_WRITE | RIGHT_FD_ALLOCATE | RIGHT_PATH_FILESTAT_SET_SIZE)
// Some runtimes have very strict expectations when it comes to which
// rights can be enabled on files opened by path_open. The fileRights
// constant is used as a mask to retain only bits for operations that
// are supported on files.
fileRights rights = RIGHT_FD_DATASYNC |
RIGHT_FD_READ |
RIGHT_FD_SEEK |
RIGHT_FDSTAT_SET_FLAGS |
RIGHT_FD_SYNC |
RIGHT_FD_TELL |
RIGHT_FD_WRITE |
RIGHT_FD_ADVISE |
RIGHT_FD_ALLOCATE |
RIGHT_PATH_CREATE_DIRECTORY |
RIGHT_PATH_CREATE_FILE |
RIGHT_PATH_LINK_SOURCE |
RIGHT_PATH_LINK_TARGET |
RIGHT_PATH_OPEN |
RIGHT_FD_READDIR |
RIGHT_PATH_READLINK |
RIGHT_PATH_RENAME_SOURCE |
RIGHT_PATH_RENAME_TARGET |
RIGHT_PATH_FILESTAT_GET |
RIGHT_PATH_FILESTAT_SET_SIZE |
RIGHT_PATH_FILESTAT_SET_TIMES |
RIGHT_FD_FILESTAT_GET |
RIGHT_FD_FILESTAT_SET_SIZE |
RIGHT_FD_FILESTAT_SET_TIMES |
RIGHT_PATH_SYMLINK |
RIGHT_PATH_REMOVE_DIRECTORY |
RIGHT_PATH_UNLINK_FILE |
RIGHT_POLL_FD_READWRITE
// Runtimes like wasmtime and wasmedge will refuse to open directories
// if the rights requested by the application exceed the operations that
// can be performed on a directory.
dirRights rights = RIGHT_FD_SEEK |
RIGHT_FDSTAT_SET_FLAGS |
RIGHT_FD_SYNC |
RIGHT_PATH_CREATE_DIRECTORY |
RIGHT_PATH_CREATE_FILE |
RIGHT_PATH_LINK_SOURCE |
RIGHT_PATH_LINK_TARGET |
RIGHT_PATH_OPEN |
RIGHT_FD_READDIR |
RIGHT_PATH_READLINK |
RIGHT_PATH_RENAME_SOURCE |
RIGHT_PATH_RENAME_TARGET |
RIGHT_PATH_FILESTAT_GET |
RIGHT_PATH_FILESTAT_SET_SIZE |
RIGHT_PATH_FILESTAT_SET_TIMES |
RIGHT_FD_FILESTAT_GET |
RIGHT_FD_FILESTAT_SET_TIMES |
RIGHT_PATH_SYMLINK |
RIGHT_PATH_REMOVE_DIRECTORY |
RIGHT_PATH_UNLINK_FILE
)
// https://github.com/WebAssembly/WASI/blob/a2b96e81c0586125cc4dc79a5be0b78d9a059925/legacy/preview1/docs.md#-fd_closefd-fd---result-errno
@ -435,11 +492,11 @@ func Open(path string, openmode int, perm uint32) (int, error) {
var rights rights
switch openmode & (O_RDONLY | O_WRONLY | O_RDWR) {
case O_RDONLY:
rights = fullRights & ^writeRights
rights = fileRights & ^writeRights
case O_WRONLY:
rights = fullRights & ^readRights
rights = fileRights & ^readRights
case O_RDWR:
rights = fullRights
rights = fileRights
}
var fdflags fdflags
@ -458,10 +515,32 @@ func Open(path string, openmode int, perm uint32) (int, error) {
pathLen,
oflags,
rights,
fullRights,
fileRights,
fdflags,
unsafe.Pointer(&fd),
)
if errno == EISDIR && oflags == 0 && fdflags == 0 && ((rights & writeRights) == 0) {
// wasmtime and wasmedge will error if attempting to open a directory
// because we are asking for too many rights. However, we cannot
// determine ahread of time if the path we are about to open is a
// directory, so instead we fallback to a second call to path_open with
// a more limited set of rights.
//
// This approach is subject to a race if the file system is modified
// concurrently, so we also inject OFLAG_DIRECTORY to ensure that we do
// not accidentally open a file which is not a directory.
errno = path_open(
dirFd,
LOOKUP_SYMLINK_FOLLOW,
pathPtr,
pathLen,
oflags|OFLAG_DIRECTORY,
rights&dirRights,
fileRights,
fdflags,
unsafe.Pointer(&fd),
)
}
return int(fd), errnoErr(errno)
}