qemu/qemu.git/fsdev, branch master

hw/9pfs: add max_xattr option

2026-06-29T13:10:31+00:00

Previous patch introduced a limit of max. 1024 simultaneous xattr FIDs. This patch introduces an option "max_attr" that allows to override this limit, just for the case that some user might run into this limit for some reason, even if unlikely; or for reducing the limit further down (e.g. that default limit of 1024 would cap at max. 64 MiB host memory, at least on Linux hosts where the limit per xattr is 64k). This new "max_xattr" option can be specified with both -fsdev and -virtfs command line options, with the "local" and the "synth" fs drivers. The previous limit of 1024 is preserved as the default value. Link: https://lore.kernel.org/qemu-devel/b7631ac0d8dde0629bc7c4f2c4185d9f57b962b4.1781361555.git.qemu_oss@crudebyte.com Signed-off-by: Christian Schoenebeck

hw/9pfs: add xattr FID limit to prevent memory exhaustion

2026-06-29T13:10:31+00:00

Add a limit on the number of simultaneously open xattr FIDs to prevent host memory exhaustion attacks. Each xattr FID contains a buffer for the xattr value, and without a limit, a malicious priviliged guest with direct communication access to 9p server could create a huge number of xattr FIDs until host memory is eventually exhausted. Fix this by: - add xattr_fid_limit to struct FsContext for the max. amount - add xattr_fid_count to struct FsContext for the current amount - init xattr_fid_limit with 1024 - init xattr_fid_count with 0 - add function xattr_fid_count_inc() to increment the count - add function xattr_fid_count_decr() to decrement the count - call xattr_fid_count_inc() in Txattrcreate handler - call xattr_fid_count_inc() in Txattrwalk handler - call xattr_fid_count_decr() when a xattr FID is freed Additionally: - reset the xattr FID counter in virtfs_reset() When the limit is reached then xattr_fid_count_inc() returns -ENOSPC and the request handler is aborted on its error path without turning the FID into an xattr type and without allocating memory for the xattr. The default value of 1024 was chosen, as (sane usage of) xattr requests in the 9p protocol are usually very short-lived, and even machines with 128 cores with very high xattr activity should have plenty of head room without ever hitting this limit. Fixes: 10b468bdc5 ("virtio-9p: Implement TXATTRCREATE") Fixes: CVE-2026-8348 Reported-by: Feifan Qian Link: https://lore.kernel.org/qemu-devel/eb3787869745d47234fb662600187bf773e1ef8a.1781361555.git.qemu_oss@crudebyte.com Signed-off-by: Christian Schoenebeck

hw/9pfs: change V9fsPath.size to size_t and v9fs_path_sprintf() return type

2026-06-01T09:11:39+00:00

- Change V9fsPath.size from uint16_t to size_t to support paths larger than 65536 bytes. - Change v9fs_path_sprintf() return type from void to int to allow error reporting. Link: https://lore.kernel.org/qemu-devel/2d2348d94ff43fbe4cc0aea24fb312c5c15ee809.1779126034.git.qemu_oss@crudebyte.com Signed-off-by: Christian Schoenebeck

fsdev: Build stubs once

2026-03-17T18:50:05+00:00

Move stubs to the global stub_ss[] source set. These files are now built once for all binaries, instead of one time per system binary. Signed-off-by: Philippe Mathieu-Daudé Reviewed-by: Pierrick Bouvier Reviewed-by: Richard Henderson Message-Id: <20260225035739.42848-11-philmd@linaro.org>

block: extract include/qemu/aiocb.h out of include/block/aio.h

2025-12-27T09:11:12+00:00

Create a new header corresponding to functions defined in util/aiocb.c, and include it whenever AIOCBs are used but AioContext is not. Signed-off-by: Paolo Bonzini

9pfs: Add FreeBSD support

2025-09-18T19:21:29+00:00

This is largely derived from existing Darwin support. FreeBSD apparently has better support for *at() system calls so doesn't require workarounds for a missing mknodat(). The implementation has a couple of warts however: - The extattr(2) system calls don't support anything akin to XATTR_CREATE or XATTR_REPLACE, so a racy workaround is implemented. - Attribute names cannot begin with "user." or "system." on ZFS. However FreeBSD's extattr(2) system calls support two dedicated namespaces for these two. So "user." or "system." prefixes are trimmed off from attribute names and instead EXTATTR_NAMESPACE_USER or EXTATTR_NAMESPACE_SYSTEM are picked and passed to extattr system calls accordingly. The 9pfs tests were verified to pass on the UFS, ZFS and tmpfs filesystems. Signed-off-by: Mark Johnston Link: https://lore.kernel.org/qemu-devel/aJOWhHB2p-fbueAm@nuc Signed-off-by: Christian Schoenebeck

fsdev/9p-marshal: move G_GNUC_PRINTF to header

2025-07-16T12:18:48+00:00

v9fs_string_sprintf() is annotated with G_GNUC_PRINTF(2, 3) in 9p-marshal.c, but the prototype in fsdev/9p-marshal.h is missing the attribute, so callers that include only the header do not get format checking. Move the annotation to the header and delete the duplicate in the source file. No behavior change. Signed-off-by: Sean Wei Reviewed-by: Philippe Mathieu-Daudé Message-Id: <20250613.qemu.9p.01@sean.taipei> [CS: fix code style (max. 80 chars per line)] Signed-off-by: Christian Schoenebeck

9pfs: Introduce futimens file op

2025-05-05T09:28:29+00:00

Add an futimens operation to the fs driver and use if when a fid has a valid file descriptor. This is required to support more cases where the client wants to do an action on an unlinked file which it still has an open file decriptor for. Only 9P2000.L was considered. Signed-off-by: Greg Kurz Reviewed-by: Christian Schoenebeck Message-Id: <20250312152933.383967-5-groug@kaod.org> Signed-off-by: Christian Schoenebeck

9pfs: Introduce ftruncate file op

2025-05-05T09:28:29+00:00

Add an ftruncate operation to the fs driver and use if when a fid has a valid file descriptor. This is required to support more cases where the client wants to do an action on an unlinked file which it still has an open file decriptor for. Only 9P2000.L was considered. Signed-off-by: Greg Kurz Reviewed-by: Christian Schoenebeck Message-Id: <20250312152933.383967-4-groug@kaod.org> Signed-off-by: Christian Schoenebeck

9pfs: Don't use file descriptors in core code

2025-05-05T09:28:29+00:00

v9fs_getattr() currently peeks into V9fsFidOpenState to know if a fid has a valid file descriptor or directory stream. Even though the fields are accessible, this is an implementation detail of the local backend that should not be manipulated directly by the server code. Abstract that with a new has_valid_file_handle() backend operation. Signed-off-by: Greg Kurz Reviewed-by: Christian Schoenebeck Message-Id: <20250312152933.383967-3-groug@kaod.org> Signed-off-by: Christian Schoenebeck