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virtiofsd: Fix xattr operations

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Current virtiofsd has problems about xattr operations and
they does not work properly for directory/symlink/special file.

The fundamental cause is that virtiofsd uses openat() + f...xattr()
systemcalls for xattr operation but we should not open symlink/special
file in the daemon. Therefore the function is restricted.

Fix this problem by:
 1. during setup of each thread, call unshare(CLONE_FS)
 2. in xattr operations (i.e. lo_getxattr), if inode is not a regular
    file or directory, use fchdir(proc_loot_fd) + ...xattr() +
    fchdir(root.fd) instead of openat() + f...xattr()

    (Note: for a regular file/directory openat() + f...xattr()
     is still used for performance reason)

With this patch, xfstests generic/062 passes on virtiofs.

This fix is suggested by Miklos Szeredi and Stefan Hajnoczi.
The original discussion can be found here:
  https://www.redhat.com/archives/virtio-fs/2019-October/msg00046.html

Signed-off-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Message-Id: <20200227055927.24566-3-misono.tomohiro@jp.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Misono Tomohiro 2020-02-27 14:59:27 +09:00 • committed by Dr. David Alan Gilbert
parent 16e15a7308
commit bdfd667883
3 changed files with 77 additions and 47 deletions
Download patch file Download diff file Expand all files Collapse all files

6
tools/virtiofsd/seccomp.c
View file

@ -41,6 +41,7 @@ static const int syscall_whitelist[] = {
SCMP_SYS(exit),
SCMP_SYS(exit_group),
SCMP_SYS(fallocate),
SCMP_SYS(fchdir),
SCMP_SYS(fchmodat),
SCMP_SYS(fchownat),
SCMP_SYS(fcntl),
@ -62,7 +63,9 @@ static const int syscall_whitelist[] = {
SCMP_SYS(getpid),
SCMP_SYS(gettid),
SCMP_SYS(gettimeofday),
SCMP_SYS(getxattr),
SCMP_SYS(linkat),
SCMP_SYS(listxattr),
SCMP_SYS(lseek),
SCMP_SYS(madvise),
SCMP_SYS(mkdirat),
@ -85,6 +88,7 @@ static const int syscall_whitelist[] = {
SCMP_SYS(recvmsg),
SCMP_SYS(renameat),
SCMP_SYS(renameat2),
SCMP_SYS(removexattr),
SCMP_SYS(rt_sigaction),
SCMP_SYS(rt_sigprocmask),
SCMP_SYS(rt_sigreturn),
@ -98,10 +102,12 @@ static const int syscall_whitelist[] = {
SCMP_SYS(setresuid32),
#endif
SCMP_SYS(set_robust_list),
SCMP_SYS(setxattr),
SCMP_SYS(symlinkat),
SCMP_SYS(time), /* Rarely needed, except on static builds */
SCMP_SYS(tgkill),
SCMP_SYS(unlinkat),
SCMP_SYS(unshare),
SCMP_SYS(utimensat),
SCMP_SYS(write),
SCMP_SYS(writev),