fix Wasi rights system to work with wasi-libc #6463
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alexcrichton
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implementations such as wasi-libc use these as a mask for any rights they request for a new fd when invoking path_open
…am creation which will mean editing the wit.
…n error-code in order to fail appropriately when a file is not open for reading or writing.
I appreciate his work on this stuff in the past but he hasnt been around for a few years now
since file perms is now more accurately the file's access mode, a file open for writing was having problems here. in reality i dont think it makes sense to restrict this based on the perms. if a file is opened, you should be able to stat it. this fixes the host adapter's path_link test, which was broken by prior changes. additionally, this fix lets the path_open_dirfd_not_dir test pass.
in order to work with wasi-testsuite, it needs to be possible to path_open(dirfd, ".", ...) with the same rights reported in the fdstat of that dirfd. When we report the Rights::all() set, both FD_READ and FD_WRITE are set in the base rights, which results in unix rejecting an openat2(dirfd, ".", O_RDWR) with EISDIR. By not having the FD_READ and FD_WRITE rights present in the base rights, the open syscall defaults to O_RDONLY, which is the only access mode allowed for opening directories.
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* wasi-common: need FileEntry to track the mode with which a file was opened
* add a test for read, write access modes in path_open
* a directory needs to report full set of rights in fdstat
implementations such as wasi-libc use these as a mask for any rights
they request for a new fd when invoking path_open
* preview2: mask file perms. and we really need to enforce them on stream creation
which will mean editing the wit.
* filesystem.wit: make {read, write, append}-via-stream fallible with an error-code
in order to fail appropriately when a file is not open for reading or
writing.
* filesystem.wit: update comments
* preview2 impls: fix error handling for {read,write,append}_via_stream
* wasi-common: normalize wrong access mode error on windows to badf
* remove kubkob from labeler
I appreciate his work on this stuff in the past but he hasnt been around
for a few years now
* preview 2 filesystem: allow stat on any opened fd
since file perms is now more accurately the file's access mode, a file
open for writing was having problems here.
in reality i dont think it makes sense to restrict this based on the
perms. if a file is opened, you should be able to stat it.
this fixes the host adapter's path_link test, which was broken by prior
changes. additionally, this fix lets the path_open_dirfd_not_dir test
pass.
* fix the directory base & inheriting rights
in order to work with wasi-testsuite, it needs to be possible to
path_open(dirfd, ".", ...) with the same rights reported in the
fdstat of that dirfd. When we report the Rights::all() set, both
FD_READ and FD_WRITE are set in the base rights, which results in
unix rejecting an openat2(dirfd, ".", O_RDWR) with EISDIR.
By not having the FD_READ and FD_WRITE rights present in the base
rights, the open syscall defaults to O_RDONLY, which is the only
access mode allowed for opening directories.
* path_open of a directory with read and write succeeds on windows
|
The bug that this fixed has regressed in certain ways. Reproduction here: WebAssembly/wasi-libc#415 (comment) |
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This is an upstreaming of #6462
#6265 introduced a regression with programs using wasi-libc, reported at WebAssembly/wasi-libc#415.
Wasi-libc read the rights of the base directory (using fd_fdstat_get) and used those to mask the rights requested to path_open. In 6265, I changed the behavior of fdstat_get to always report and empty set of rights. This means that Wasi-libc will always pass an empty set of rights to path_open, which is a problem because the FD_READ and FD_WRITE rights are how path_open determines if a descriptor is to be opened for reading, writing, or both.
The fix is as follows:
Preview 2's wit definition was unintentionally (per @sunfishcode) missing a way for
filesystem.{read,write,append}-via-streamto return anerror-codewhen a descriptor cannot be used to create such a stream. I added this to the wit definition in order to make the preview 2 behavior match the legacy implementation.