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9pfs: fix wrong encoding of rdev field in Rgetattr on macOS

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The 'rdev' field in 9p reponse 'Rgetattr' is of type dev_t,
which is actually a system dependant type and therefore both the
size and encoding of dev_t differ between macOS and Linux.

So far we have sent 'rdev' to guest in host's dev_t format as-is,
which caused devices to appear with wrong device numbers on
guests running on macOS hosts, eventually leading to various
misbehaviours on guest in conjunction with device files.

This patch fixes this issue by converting the device number from
host's dev_t format to Linux dev_t format. As 9p request
'Tgettattr' is exclusive to protocol version 9p2000.L, it should
be fair to assume that 'rdev' field is assumed to be in Linux dev_t
format by client as well.

Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Link: https://lore.kernel.org/qemu-devel/20220421093056.5ab1e7ed@bahia/
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Message-Id: <b3a430c2c382ba69a7405e04c0b090ab0d86f17e.1651228001.git.qemu_oss@crudebyte.com>
This commit is contained in:
Christian Schoenebeck 2022-04-29 12:25:15 +02:00
parent 055ab89327
commit e5c88e2264
2 changed files with 40 additions and 1 deletions
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39
hw/9pfs/9p-util.h
View File

@ -19,6 +19,45 @@
#define O_PATH_9P_UTIL 0
#endif
#if !defined(CONFIG_LINUX)
/*
* Generates a Linux device number (a.k.a. dev_t) for given device major
* and minor numbers.
*
* To be more precise: it generates a device number in glibc's format
* (MMMM_Mmmm_mmmM_MMmm, 64 bits) actually, which is compatible with
* Linux's format (mmmM_MMmm, 32 bits), as described in <bits/sysmacros.h>.
*/
static inline uint64_t makedev_dotl(uint32_t dev_major, uint32_t dev_minor)
{
uint64_t dev;
// from glibc sysmacros.h:
dev = (((uint64_t) (dev_major & 0x00000fffu)) << 8);
dev |= (((uint64_t) (dev_major & 0xfffff000u)) << 32);
dev |= (((uint64_t) (dev_minor & 0x000000ffu)) << 0);
dev |= (((uint64_t) (dev_minor & 0xffffff00u)) << 12);
return dev;
}
#endif
/*
* Converts given device number from host's device number format to Linux
* device number format. As both the size of type dev_t and encoding of
* dev_t is system dependant, we have to convert them for Linux guests if
* host is not running Linux.
*/
static inline uint64_t host_dev_to_dotl_dev(dev_t dev)
{
#ifdef CONFIG_LINUX
return dev;
#else
return makedev_dotl(major(dev), minor(dev));
#endif
}
#ifdef CONFIG_DARWIN
#define qemu_fgetxattr(...) fgetxattr(__VA_ARGS__, 0, 0)
#define qemu_lgetxattr(...) getxattr(__VA_ARGS__, 0, XATTR_NOFOLLOW)

2
hw/9pfs/9p.c
View File

@ -1327,7 +1327,7 @@ static int stat_to_v9stat_dotl(V9fsPDU *pdu, const struct stat *stbuf,
v9lstat->st_nlink = stbuf->st_nlink;
v9lstat->st_uid = stbuf->st_uid;
v9lstat->st_gid = stbuf->st_gid;
v9lstat->st_rdev = stbuf->st_rdev;
v9lstat->st_rdev = host_dev_to_dotl_dev(stbuf->st_rdev);
v9lstat->st_size = stbuf->st_size;
v9lstat->st_blksize = stat_to_iounit(pdu, stbuf);
v9lstat->st_blocks = stbuf->st_blocks;