qemu-kvm/SOURCES/kvm-virtiofsd-passthrough_ll-create-new-files-in-caller-.patch

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From af14ef1dba9356e566c9c7531b8fd23361c2b16d Mon Sep 17 00:00:00 2001
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Mon, 27 Jan 2020 19:01:12 +0100
Subject: [PATCH 041/116] virtiofsd: passthrough_ll: create new files in
caller's context
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: <20200127190227.40942-38-dgilbert@redhat.com>
Patchwork-id: 93488
O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 037/112] virtiofsd: passthrough_ll: create new files in caller's context
Bugzilla: 1694164
RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Sergio Lopez Pascual <slp@redhat.com>
From: Vivek Goyal <vgoyal@redhat.com>
We need to create files in the caller's context. Otherwise after
creating a file, the caller might not be able to do file operations on
that file.
Changed effective uid/gid to caller's uid/gid, create file and then
switch back to uid/gid 0.
Use syscall(setresuid, ...) otherwise glibc does some magic to change EUID
in all threads, which is not what we want.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
(cherry picked from commit 929cfb7a9a1b101cdfc9ac19807ecab4c81a13e4)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
tools/virtiofsd/passthrough_ll.c | 96 +++++++++++++++++++++++++++++++++++++---
1 file changed, 91 insertions(+), 5 deletions(-)
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index cd27c09..5e06179 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -50,6 +50,7 @@
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>
+#include <sys/syscall.h>
#include <sys/xattr.h>
#include <unistd.h>
@@ -83,6 +84,11 @@ struct lo_inode {
uint64_t refcount; /* protected by lo->mutex */
};
+struct lo_cred {
+ uid_t euid;
+ gid_t egid;
+};
+
enum {
CACHE_NEVER,
CACHE_NORMAL,
@@ -383,6 +389,69 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
}
}
+/*
+ * On some archs, setres*id is limited to 2^16 but they
+ * provide setres*id32 variants that allow 2^32.
+ * Others just let setres*id do 2^32 anyway.
+ */
+#ifdef SYS_setresgid32
+#define OURSYS_setresgid SYS_setresgid32
+#else
+#define OURSYS_setresgid SYS_setresgid
+#endif
+
+#ifdef SYS_setresuid32
+#define OURSYS_setresuid SYS_setresuid32
+#else
+#define OURSYS_setresuid SYS_setresuid
+#endif
+
+/*
+ * Change to uid/gid of caller so that file is created with
+ * ownership of caller.
+ * TODO: What about selinux context?
+ */
+static int lo_change_cred(fuse_req_t req, struct lo_cred *old)
+{
+ int res;
+
+ old->euid = geteuid();
+ old->egid = getegid();
+
+ res = syscall(OURSYS_setresgid, -1, fuse_req_ctx(req)->gid, -1);
+ if (res == -1) {
+ return errno;
+ }
+
+ res = syscall(OURSYS_setresuid, -1, fuse_req_ctx(req)->uid, -1);
+ if (res == -1) {
+ int errno_save = errno;
+
+ syscall(OURSYS_setresgid, -1, old->egid, -1);
+ return errno_save;
+ }
+
+ return 0;
+}
+
+/* Regain Privileges */
+static void lo_restore_cred(struct lo_cred *old)
+{
+ int res;
+
+ res = syscall(OURSYS_setresuid, -1, old->euid, -1);
+ if (res == -1) {
+ fuse_log(FUSE_LOG_ERR, "seteuid(%u): %m\n", old->euid);
+ exit(1);
+ }
+
+ res = syscall(OURSYS_setresgid, -1, old->egid, -1);
+ if (res == -1) {
+ fuse_log(FUSE_LOG_ERR, "setegid(%u): %m\n", old->egid);
+ exit(1);
+ }
+}
+
static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
const char *name, mode_t mode, dev_t rdev,
const char *link)
@@ -391,12 +460,21 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
int saverr;
struct lo_inode *dir = lo_inode(req, parent);
struct fuse_entry_param e;
+ struct lo_cred old = {};
saverr = ENOMEM;
+ saverr = lo_change_cred(req, &old);
+ if (saverr) {
+ goto out;
+ }
+
res = mknod_wrapper(dir->fd, name, link, mode, rdev);
saverr = errno;
+
+ lo_restore_cred(&old);
+
if (res == -1) {
goto out;
}
@@ -794,26 +872,34 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
struct lo_data *lo = lo_data(req);
struct fuse_entry_param e;
int err;
+ struct lo_cred old = {};
if (lo_debug(req)) {
fuse_log(FUSE_LOG_DEBUG, "lo_create(parent=%" PRIu64 ", name=%s)\n",
parent, name);
}
+ err = lo_change_cred(req, &old);
+ if (err) {
+ goto out;
+ }
+
fd = openat(lo_fd(req, parent), name, (fi->flags | O_CREAT) & ~O_NOFOLLOW,
mode);
- if (fd == -1) {
- return (void)fuse_reply_err(req, errno);
- }
+ err = fd == -1 ? errno : 0;
+ lo_restore_cred(&old);
- fi->fh = fd;
+ if (!err) {
+ fi->fh = fd;
+ err = lo_do_lookup(req, parent, name, &e);
+ }
if (lo->cache == CACHE_NEVER) {
fi->direct_io = 1;
} else if (lo->cache == CACHE_ALWAYS) {
fi->keep_cache = 1;
}
- err = lo_do_lookup(req, parent, name, &e);
+out:
if (err) {
fuse_reply_err(req, err);
} else {
--
1.8.3.1