[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PATCH v4 02/12] virtiofsd: Limit setxattr()'s creds-dropped region
From: |
Hanna Reitz |
Subject: |
[PATCH v4 02/12] virtiofsd: Limit setxattr()'s creds-dropped region |
Date: |
Thu, 16 Sep 2021 10:40:35 +0200 |
We only need to drop/switch our credentials for the (f)setxattr() call
alone, not for the openat() or fchdir() around it.
(Right now, this may not be that big of a problem, but with inodes being
identified by file handles instead of an O_PATH fd, we will need
open_by_handle_at() calls here, which is really fickle when it comes to
credentials being dropped.)
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
---
tools/virtiofsd/passthrough_ll.c | 34 +++++++++++++++++++++++---------
1 file changed, 25 insertions(+), 9 deletions(-)
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 6511a6acb4..b43afdfbd3 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -3123,6 +3123,7 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino,
const char *in_name,
bool switched_creds = false;
bool cap_fsetid_dropped = false;
struct lo_cred old = {};
+ bool changed_cwd = false;
if (block_xattr(lo, in_name)) {
fuse_reply_err(req, EOPNOTSUPP);
@@ -3158,6 +3159,24 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino,
const char *in_name,
", name=%s value=%s size=%zd)\n", ino, name, value, size);
sprintf(procname, "%i", inode->fd);
+ /*
+ * We can only open regular files or directories. If the inode is
+ * something else, we have to enter /proc/self/fd and use
+ * setxattr() on the link's filename there.
+ */
+ if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
+ fd = openat(lo->proc_self_fd, procname, O_RDONLY);
+ if (fd < 0) {
+ saverr = errno;
+ goto out;
+ }
+ } else {
+ /* fchdir should not fail here */
+ FCHDIR_NOFAIL(lo->proc_self_fd);
+ /* Set flag so the clean-up path will chdir back */
+ changed_cwd = true;
+ }
+
/*
* If we are setting posix access acl and if SGID needs to be
* cleared, then switch to caller's gid and drop CAP_FSETID
@@ -3178,20 +3197,12 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino,
const char *in_name,
}
switched_creds = true;
}
- if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
- fd = openat(lo->proc_self_fd, procname, O_RDONLY);
- if (fd < 0) {
- saverr = errno;
- goto out;
- }
+ if (fd >= 0) {
ret = fsetxattr(fd, name, value, size, flags);
saverr = ret == -1 ? errno : 0;
} else {
- /* fchdir should not fail here */
- FCHDIR_NOFAIL(lo->proc_self_fd);
ret = setxattr(procname, name, value, size, flags);
saverr = ret == -1 ? errno : 0;
- FCHDIR_NOFAIL(lo->root.fd);
}
if (switched_creds) {
if (cap_fsetid_dropped)
@@ -3201,6 +3212,11 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino,
const char *in_name,
}
out:
+ if (changed_cwd) {
+ /* Change CWD back, fchdir should not fail here */
+ FCHDIR_NOFAIL(lo->root.fd);
+ }
+
if (fd >= 0) {
close(fd);
}
--
2.31.1
- [PATCH v4 00/12] virtiofsd: Allow using file handles instead of O_PATH FDs, Hanna Reitz, 2021/09/16
- [PATCH v4 01/12] virtiofsd: Keep /proc/self/mountinfo open, Hanna Reitz, 2021/09/16
- [PATCH v4 02/12] virtiofsd: Limit setxattr()'s creds-dropped region,
Hanna Reitz <=
- [PATCH v4 03/12] virtiofsd: Add TempFd structure, Hanna Reitz, 2021/09/16
- [PATCH v4 04/12] virtiofsd: Use lo_inode_open() instead of openat(), Hanna Reitz, 2021/09/16
- [PATCH v4 05/12] virtiofsd: Add lo_inode_fd() helper, Hanna Reitz, 2021/09/16
- [PATCH v4 06/12] virtiofsd: Let lo_fd() return a TempFd, Hanna Reitz, 2021/09/16
- [PATCH v4 07/12] virtiofsd: Let lo_inode_open() return a TempFd, Hanna Reitz, 2021/09/16
- [PATCH v4 08/12] virtiofsd: Pass lo_data to lo_inode_{fd,open}(), Hanna Reitz, 2021/09/16
- [PATCH v4 09/12] virtiofsd: Add lo_inode.fhandle, Hanna Reitz, 2021/09/16
- [PATCH v4 10/12] virtiofsd: Add inodes_by_handle hash table, Hanna Reitz, 2021/09/16
- [PATCH v4 11/12] virtiofsd: Optionally fill lo_inode.fhandle, Hanna Reitz, 2021/09/16
- [PATCH v4 12/12] virtiofsd: Add lazy lo_do_find(), Hanna Reitz, 2021/09/16