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hostfs: fix dev_t handling

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dev_t is a kernel type and may have different definitions
in kernel and userspace. On 32-bit x86 this currently makes
the stat structure being 4 bytes longer in the user code,
causing stack corruption.

However, this is (potentially) not the only problem, since
dev_t is a different type on user/kernel side, so we don't
know that the major/minor encoding isn't also different.
Decode/encode it instead to address both problems.

Cc: stable@vger.kernel.org
Fixes: 74ce793bcb ("hostfs: Fix ephemeral inodes")
Link: https://patch.msgid.link/20240702092440.acc960585dd5.Id0767e12f562a69c6cd3c3262dc3d765db350cf6@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Johannes Berg 2024-07-02 09:24:41 +02:00
parent 53585f9ea4
commit 267ed02c21
3 changed files with 14 additions and 10 deletions
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7
fs/hostfs/hostfs.h
View file

@ -63,9 +63,10 @@ struct hostfs_stat {
struct hostfs_timespec atime, mtime, ctime;
unsigned int blksize;
unsigned long long blocks;
unsigned int maj;
unsigned int min;
dev_t dev;
struct {
unsigned int maj;
unsigned int min;
} rdev, dev;
};
extern int stat_file(const char *path, struct hostfs_stat *p, int fd);

10
fs/hostfs/hostfs_kern.c
View file

@ -530,10 +530,11 @@ static int hostfs_inode_update(struct inode *ino, const struct hostfs_stat *st)
static int hostfs_inode_set(struct inode *ino, void *data)
{
struct hostfs_stat *st = data;
dev_t rdev;
dev_t dev, rdev;
/* Reencode maj and min with the kernel encoding.*/
rdev = MKDEV(st->maj, st->min);
rdev = MKDEV(st->rdev.maj, st->rdev.min);
dev = MKDEV(st->dev.maj, st->dev.min);
switch (st->mode & S_IFMT) {
case S_IFLNK:
@ -559,7 +560,7 @@ static int hostfs_inode_set(struct inode *ino, void *data)
return -EIO;
}
HOSTFS_I(ino)->dev = st->dev;
HOSTFS_I(ino)->dev = dev;
ino->i_ino = st->ino;
ino->i_mode = st->mode;
return hostfs_inode_update(ino, st);
@ -568,8 +569,9 @@ static int hostfs_inode_set(struct inode *ino, void *data)
static int hostfs_inode_test(struct inode *inode, void *data)
{
const struct hostfs_stat *st = data;
dev_t dev = MKDEV(st->dev.maj, st->dev.min);
return inode->i_ino == st->ino && HOSTFS_I(inode)->dev == st->dev;
return inode->i_ino == st->ino && HOSTFS_I(inode)->dev == dev;
}
static struct inode *hostfs_iget(struct super_block *sb, char *name)

7
fs/hostfs/hostfs_user.c
View file

@ -34,9 +34,10 @@ static void stat64_to_hostfs(const struct stat64 *buf, struct hostfs_stat *p)
p->mtime.tv_nsec = 0;
p->blksize = buf->st_blksize;
p->blocks = buf->st_blocks;
p->maj = os_major(buf->st_rdev);
p->min = os_minor(buf->st_rdev);
p->dev = buf->st_dev;
p->rdev.maj = os_major(buf->st_rdev);
p->rdev.min = os_minor(buf->st_rdev);
p->dev.maj = os_major(buf->st_dev);
p->dev.min = os_minor(buf->st_dev);
}
int stat_file(const char *path, struct hostfs_stat *p, int fd)