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Switch to check for effective user id in r349320, and disable dumping

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into existing files for sugid processes.

Despite using real user id pronounces the intent, it actually breaks
suid coredumps, while not making any difference for non-sugid
processes.  The reason for the breakage is that non-existent core file
is created with the effective uid (unless weird hacks like SUIDDIR are
configured).

Then, if user enabled kern.sugid_coredump, core dumping should not
overwrite core files owned by effective uid, but we cannot pretend to
use real uid for dumping.

PR:	68905
admbugs:	358
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2019-06-23 21:15:31 +00:00
parent 22c7bcb842
commit 89f2ab0608
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=349324
1 changed files with 13 additions and 5 deletions
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18
sys/kern/kern_sig.c
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@ -3398,10 +3398,16 @@ corefile_open_last(struct thread *td, char *name, int indexpos,
}
if (oldvp != NULL) {
if (nextvp == NULL)
nextvp = oldvp;
else
if (nextvp == NULL) {
if ((td->td_proc->p_flag & P_SUGID) != 0) {
error = EFAULT;
vnode_close_locked(td, oldvp);
} else {
nextvp = oldvp;
}
} else {
vnode_close_locked(td, oldvp);
}
}
if (error != 0) {
if (nextvp != NULL)
@ -3521,6 +3527,8 @@ corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
oflags = VN_OPEN_NOAUDIT | VN_OPEN_NAMECACHE |
(capmode_coredump ? VN_OPEN_NOCAPCHECK : 0);
flags = O_CREAT | FWRITE | O_NOFOLLOW;
if ((td->td_proc->p_flag & P_SUGID) != 0)
flags |= O_EXCL;
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, td);
error = vn_open_cred(&nd, &flags, cmode, oflags, td->td_ucred,
@ -3597,11 +3605,11 @@ coredump(struct thread *td)
/*
* Don't dump to non-regular files or files with links.
* Do not dump into system files. Real user must own the corefile.
* Do not dump into system files. Effective user must own the corefile.
*/
if (vp->v_type != VREG || VOP_GETATTR(vp, &vattr, cred) != 0 ||
vattr.va_nlink != 1 || (vp->v_vflag & VV_SYSTEM) != 0 ||
vattr.va_uid != cred->cr_ruid) {
vattr.va_uid != cred->cr_uid) {
VOP_UNLOCK(vp, 0);
error = EFAULT;
goto out;