mirrors/qemu
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

virtfs-proxy-helper: use setresuid and setresgid

Browse Source 
The setfsuid and setfsgid system calls are obscure and they complicate
the error checking (that glibc's warn_unused_result "feature" forces
us to do).  Switch to the standard setresuid and setresgid functions.

Signed-off-by: Paolo Bonzini <pbonini@redhat.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
This commit is contained in:
Paolo Bonzini 2012-10-11 14:20:23 +02:00 committed by Aneesh Kumar K.V
parent 16c6c80ac3
commit 9fd2ecdc8c
1 changed files with 64 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

91
fsdev/virtfs-proxy-helper.c
View File

@ -272,16 +272,23 @@ static int send_status(int sockfd, struct iovec *iovec, int status)
/*
* from man 7 capabilities, section
* Effect of User ID Changes on Capabilities:
* 4. If the file system user ID is changed from 0 to nonzero (see setfsuid(2))
* then the following capabilities are cleared from the effective set:
* CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH, CAP_FOWNER, CAP_FSETID,
* CAP_LINUX_IMMUTABLE (since Linux 2.2.30), CAP_MAC_OVERRIDE, and CAP_MKNOD
* (since Linux 2.2.30). If the file system UID is changed from nonzero to 0,
* then any of these capabilities that are enabled in the permitted set
* are enabled in the effective set.
* If the effective user ID is changed from nonzero to 0, then the permitted
* set is copied to the effective set. If the effective user ID is changed
* from 0 to nonzero, then all capabilities are are cleared from the effective
* set.
*
* The setfsuid/setfsgid man pages warn that changing the effective user ID may
* expose the program to unwanted signals, but this is not true anymore: for an
* unprivileged (without CAP_KILL) program to send a signal, the real or
* effective user ID of the sending process must equal the real or saved user
* ID of the target process. Even when dropping privileges, it is enough to
* keep the saved UID to a "privileged" value and virtfs-proxy-helper won't
* be exposed to signals. So just use setresuid/setresgid.
*/
static int setfsugid(int uid, int gid)
static int setugid(int uid, int gid, int *suid, int *sgid)
{
int retval;
/*
* We still need DAC_OVERRIDE because we don't change
* supplementary group ids, and hence may be subjected DAC rules
@ -290,13 +297,51 @@ static int setfsugid(int uid, int gid)
CAP_DAC_OVERRIDE,
};
setfsgid(gid);
setfsuid(uid);
*suid = geteuid();
*sgid = getegid();
if (setresgid(-1, gid, *sgid) == -1) {
retval = -errno;
goto err_out;
}
if (setresuid(-1, uid, *suid) == -1) {
retval = -errno;
goto err_sgid;
}
if (uid != 0 || gid != 0) {
return do_cap_set(cap_list, ARRAY_SIZE(cap_list), 0);
if (do_cap_set(cap_list, ARRAY_SIZE(cap_list), 0) < 0) {
retval = -errno;
goto err_suid;
}
}
return 0;
err_suid:
if (setresuid(-1, *suid, *suid) == -1) {
abort();
}
err_sgid:
if (setresgid(-1, *sgid, *sgid) == -1) {
abort();
}
err_out:
return retval;
}
/*
* This is used to reset the ugid back with the saved values
* There is nothing much we can do checking error values here.
*/
static void resetugid(int suid, int sgid)
{
if (setresgid(-1, sgid, sgid) == -1) {
abort();
}
if (setresuid(-1, suid, suid) == -1) {
abort();
}
}
/*
@ -578,18 +623,15 @@ static int do_create_others(int type, struct iovec *iovec)
v9fs_string_init(&path);
v9fs_string_init(&oldpath);
cur_uid = geteuid();
cur_gid = getegid();
retval = proxy_unmarshal(iovec, offset, "dd", &uid, &gid);
if (retval < 0) {
return retval;
}
offset += retval;
retval = setfsugid(uid, gid);
retval = setugid(uid, gid, &cur_uid, &cur_gid);
if (retval < 0) {
retval = -errno;
goto err_out;
goto unmarshal_err_out;
}
switch (type) {
case T_MKNOD:
@ -619,9 +661,10 @@ static int do_create_others(int type, struct iovec *iovec)
}
err_out:
resetugid(cur_uid, cur_gid);
unmarshal_err_out:
v9fs_string_free(&path);
v9fs_string_free(&oldpath);
setfsugid(cur_uid, cur_gid);
return retval;
}
@ -641,24 +684,16 @@ static int do_create(struct iovec *iovec)
if (ret < 0) {
goto unmarshal_err_out;
}
cur_uid = geteuid();
cur_gid = getegid();
ret = setfsugid(uid, gid);
ret = setugid(uid, gid, &cur_uid, &cur_gid);
if (ret < 0) {
/*
* On failure reset back to the
* old uid/gid
*/
ret = -errno;
goto err_out;
goto unmarshal_err_out;
}
ret = open(path.data, flags, mode);
if (ret < 0) {
ret = -errno;
}
err_out:
setfsugid(cur_uid, cur_gid);
resetugid(cur_uid, cur_gid);
unmarshal_err_out:
v9fs_string_free(&path);
return ret;