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hw/9pfs: Preserve S_ISGID

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In passthrough security model in local fs driver, after a file creation
chown and chmod are done to set the file credentials and mode as requested
by 9p client. But if there was a request to create a file with S_ISGID
bit, doing chown on that file resets the S_ISGID bit. So first call
chown and then invoking chmod with proper mode bit retains the S_ISGID
(if present/requested)

This resulted in LTP mknod02, mknod03, mknod05, open10 test case
failures. This patch fixes this issue.

man 2 chown
When the owner or group of an executable file are changed by an unprivileged
user the S_ISUID  and  S_ISGID mode  bits are cleared.  POSIX does not specify
whether this also should happen when root does the chown(); the Linux behavior
depends on the kernel version.

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
This commit is contained in:
M. Mohan Kumar 2012-01-19 12:21:12 +05:30 committed by Aneesh Kumar K.V
parent 2c30dd744a
commit 2d40564aaa
2 changed files with 6 additions and 5 deletions
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4
hw/9pfs/virtio-9p-handle.c
View File

@ -63,11 +63,11 @@ static int handle_update_file_cred(int dirfd, const char *name, FsCred *credp)
if (fd < 0) {
return fd;
}
ret = fchmod(fd, credp->fc_mode & 07777);
ret = fchownat(fd, "", credp->fc_uid, credp->fc_gid, AT_EMPTY_PATH);
if (ret < 0) {
goto err_out;
}
ret = fchownat(fd, "", credp->fc_uid, credp->fc_gid, AT_EMPTY_PATH);
ret = fchmod(fd, credp->fc_mode & 07777);
err_out:
close(fd);
return ret;

7
hw/9pfs/virtio-9p-local.c
View File

@ -257,9 +257,6 @@ static int local_post_create_passthrough(FsContext *fs_ctx, const char *path,
{
char buffer[PATH_MAX];
if (chmod(rpath(fs_ctx, path, buffer), credp->fc_mode & 07777) < 0) {
return -1;
}
if (lchown(rpath(fs_ctx, path, buffer), credp->fc_uid,
credp->fc_gid) < 0) {
/*
@ -270,6 +267,10 @@ static int local_post_create_passthrough(FsContext *fs_ctx, const char *path,
return -1;
}
}
if (chmod(rpath(fs_ctx, path, buffer), credp->fc_mode & 07777) < 0) {
return -1;
}
return 0;
}