9pfs: fix regression regarding CVE-2023-2861

The released fix for this CVE:

f6b0de53fb8 ("9pfs: prevent opening special files (CVE-2023-2861)")

caused a regression with security_model=passthroug

9pfs: fix regression regarding CVE-2023-2861

The released fix for this CVE:

f6b0de53fb8 ("9pfs: prevent opening special files (CVE-2023-2861)")

caused a regression with security_model=passthrough. When handling a
'Tmknod' request there was a side effect that 'Tmknod' request could fail
as 9p server was trying to adjust permissions:

#6 close_if_special_file (fd=30) at ../hw/9pfs/9p-util.h:140
#7 openat_file (mode=<optimized out>, flags=2228224,
name=<optimized out>, dirfd=<optimized out>) at
../hw/9pfs/9p-util.h:181
#8 fchmodat_nofollow (dirfd=dirfd@entry=31,
name=name@entry=0x5555577ea6e0 "mysocket", mode=493) at
../hw/9pfs/9p-local.c:360
#9 local_set_cred_passthrough (credp=0x7ffbbc4ace10, name=0x5555577ea6e0
"mysocket", dirfd=31, fs_ctx=0x55555811f528) at
../hw/9pfs/9p-local.c:457
#10 local_mknod (fs_ctx=0x55555811f528, dir_path=<optimized out>,
name=0x5555577ea6e0 "mysocket", credp=0x7ffbbc4ace10) at
../hw/9pfs/9p-local.c:702
#11 v9fs_co_mknod (pdu=pdu@entry=0x555558121140,
fidp=fidp@entry=0x5555574c46c0, name=name@entry=0x7ffbbc4aced0,
uid=1000, gid=1000, dev=<optimized out>, mode=49645,
stbuf=0x7ffbbc4acef0) at ../hw/9pfs/cofs.c:205
#12 v9fs_mknod (opaque=0x555558121140) at ../hw/9pfs/9p.c:3711

That's because server was opening the special file to adjust permissions,
however it was using O_PATH and it would have not returned the file
descriptor to guest. So the call to close_if_special_file() on that branch
was incorrect.

Let's lift the restriction introduced by f6b0de53fb8 such that it would
allow to open special files on host if O_PATH flag is supplied, not only
for 9p server's own operations as described above, but also for any client
'Topen' request.

It is safe to allow opening special files with O_PATH on host, because
O_PATH only allows path based operations on the resulting file descriptor
and prevents I/O such as read() and write() on that file descriptor.

Fixes: f6b0de53fb8 ("9pfs: prevent opening special files (CVE-2023-2861)")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2337
Reported-by: Dirk Herrendorfer <d.herrendoerfer@de.ibm.com>
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Tested-by: Dirk Herrendorfer <d.herrendoerfer@de.ibm.com>
Message-Id: <E1tJWbk-007BH4-OB@kylie.crudebyte.com>
(cherry picked from commit d06a9d843fb65351e0e4dc42ba0c404f01ea92b3)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

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9pfs: fix 'Tgetattr' after unlink

With a valid file ID (FID) of an open file, it should be possible to send
a 'Tgettattr' 9p request and successfully receive a 'Rgetattr' response,
even if the file

9pfs: fix 'Tgetattr' after unlink

With a valid file ID (FID) of an open file, it should be possible to send
a 'Tgettattr' 9p request and successfully receive a 'Rgetattr' response,
even if the file has been removed in the meantime. Currently this would
fail with ENOENT.

I.e. this fixes the following misbehaviour with a 9p Linux client:

open("/home/tst/filename", O_RDWR|O_CREAT|O_EXCL, 0600) = 3
unlink("/home/tst/filename") = 0
fstat(3, 0x23aa1a8) = -1 ENOENT (No such file or directory)

Expected results:

open("/home/tst/filename", O_RDWR|O_CREAT|O_EXCL, 0600) = 3
unlink("/home/tst/filename") = 0
fstat(3, {st_mode=S_IFREG|0600, st_size=0, ...}) = 0

This is because 9p server is always using a path name based lstat() call
which fails as soon as the file got removed. So to fix this, use fstat()
whenever we have an open file descriptor already.

Fixes: 00ede4c2529b ("virtio-9p: getattr server implementation...")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/103
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <4c41ad47f449a5cc8bfa9285743e029080d5f324.1732465720.git.qemu_oss@crudebyte.com>

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9pfs: remove obsolete comment in v9fs_getattr()

The comment claims that we'd only support basic Tgetattr fields. This is
no longer true, so remove this comment.

Fixes: e06a765efbe3 ("hw/9pfs: Add s

9pfs: remove obsolete comment in v9fs_getattr()

The comment claims that we'd only support basic Tgetattr fields. This is
no longer true, so remove this comment.

Fixes: e06a765efbe3 ("hw/9pfs: Add st_gen support in getattr reply")
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <fb364d12045217a4c6ccd0dd6368103ddb80698b.1732465720.git.qemu_oss@crudebyte.com>

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9pfs: cleanup V9fsFidState

Drop V9fsFidState's 'next' member, which is no longer used since:

f5265c8f917e ('9pfs: use GHashTable for fid table')

Fixes: f5265c8f917e ('9pfs: use GHashTable for fi

9pfs: cleanup V9fsFidState

Drop V9fsFidState's 'next' member, which is no longer used since:

f5265c8f917e ('9pfs: use GHashTable for fid table')

Fixes: f5265c8f917e ('9pfs: use GHashTable for fid table')
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <E1tE4v2-0051EH-Ni@kylie.crudebyte.com>

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9pfs: fix crash on 'Treaddir' request

A bad (broken or malicious) 9p client (guest) could cause QEMU host to
crash by sending a 9p 'Treaddir' request with a numeric file ID (FID) that
was previously

9pfs: fix crash on 'Treaddir' request

A bad (broken or malicious) 9p client (guest) could cause QEMU host to
crash by sending a 9p 'Treaddir' request with a numeric file ID (FID) that
was previously opened for a file instead of an expected directory:

#0 0x0000762aff8f4919 in __GI___rewinddir (dirp=0xf) at
../sysdeps/unix/sysv/linux/rewinddir.c:29
#1 0x0000557b7625fb40 in do_readdir_many (pdu=0x557bb67d2eb0,
fidp=0x557bb67955b0, entries=0x762afe9fff58, offset=0, maxsize=131072,
dostat=<optimized out>) at ../hw/9pfs/codir.c:101
#2 v9fs_co_readdir_many (pdu=pdu@entry=0x557bb67d2eb0,
fidp=fidp@entry=0x557bb67955b0, entries=entries@entry=0x762afe9fff58,
offset=0, maxsize=131072, dostat=false) at ../hw/9pfs/codir.c:226
#3 0x0000557b7625c1f9 in v9fs_do_readdir (pdu=0x557bb67d2eb0,
fidp=0x557bb67955b0, offset=<optimized out>,
max_count=<optimized out>) at ../hw/9pfs/9p.c:2488
#4 v9fs_readdir (opaque=0x557bb67d2eb0) at ../hw/9pfs/9p.c:2602

That's because V9fsFidOpenState was declared as union type. So the
same memory region is used for either an open POSIX file handle (int),
or a POSIX DIR* pointer, etc., so 9p server incorrectly used the
previously opened (valid) POSIX file handle (0xf) as DIR* pointer,
eventually causing a crash in glibc's rewinddir() function.

Root cause was therefore a missing check in 9p server's 'Treaddir'
request handler, which must ensure that the client supplied FID was
really opened as directory stream before trying to access the
aforementioned union and its DIR* member.

Cc: qemu-stable@nongnu.org
Fixes: d62dbb51f7 ("virtio-9p: Add fidtype so that we can do type ...")
Reported-by: Akihiro Suda <suda.kyoto@gmail.com>
Tested-by: Akihiro Suda <suda.kyoto@gmail.com>
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <E1t8GnN-002RS8-E2@kylie.crudebyte.com>

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9p: remove 'proxy' filesystem backend driver

It has been deprecated since 8.1; remove it and suggest using the 'local' file
system backend driver instead or virtiofsd.

Acked-by: Greg Kurz <groug@ka

9p: remove 'proxy' filesystem backend driver

It has been deprecated since 8.1; remove it and suggest using the 'local' file
system backend driver instead or virtiofsd.

Acked-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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hw/xen: Make XenDevOps structures const

Keep XenDevOps structures in .rodata.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Paul Durrant <paul@xen.org>
Message-Id: <2024051

hw/xen: Make XenDevOps structures const

Keep XenDevOps structures in .rodata.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Paul Durrant <paul@xen.org>
Message-Id: <20240510104908.76908-5-philmd@linaro.org>

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