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ktrace: do not stop tracing other processes if our cannot write to this vnode

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Other processes might still be able to write, make the decision to stop
based on the per-process situation.

Reviewed by:	markj
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D30257
This commit is contained in:
Konstantin Belousov 2021-05-15 03:10:05 +03:00
parent 9bb84c23e7
commit a6144f713c
1 changed files with 19 additions and 34 deletions
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53
sys/kern/kern_ktrace.c
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@ -1190,7 +1190,7 @@ ktr_writerequest(struct thread *td, struct ktr_request *req)
struct uio auio;
struct iovec aiov[3];
struct mount *mp;
int datalen, buflen, vrele_count;
int datalen, buflen;
int error;
/*
@ -1264,44 +1264,29 @@ ktr_writerequest(struct thread *td, struct ktr_request *req)
}
/*
* If error encountered, give up tracing on this vnode. We defer
* all the vrele()'s on the vnode until after we are finished walking
* the various lists to avoid needlessly holding locks.
* NB: at this point we still hold the vnode reference that must
* not go away as we need the valid vnode to compare with. Thus let
* vrele_count start at 1 and the reference will be freed
* by the loop at the end after our last use of vp.
*/
log(LOG_NOTICE, "ktrace write failed, errno %d, tracing stopped\n",
error);
vrele_count = 1;
/*
* First, clear this vnode from being used by any processes in the
* system.
* XXX - If one process gets an EPERM writing to the vnode, should
* we really do this? Other processes might have suitable
* credentials for the operation.
* If error encountered, give up tracing on this vnode on this
* process. Other processes might still be suitable for
* writes to this vnode.
*/
p = td->td_proc;
log(LOG_NOTICE,
"ktrace write failed, errno %d, tracing stopped for pid %d\n",
error, p->p_pid);
cred = NULL;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
PROC_LOCK(p);
if (p->p_tracevp == vp) {
mtx_lock(&ktrace_mtx);
ktr_freeproc(p, &cred, NULL);
mtx_unlock(&ktrace_mtx);
vrele_count++;
}
PROC_UNLOCK(p);
if (cred != NULL) {
crfree(cred);
cred = NULL;
}
PROC_LOCK(p);
mtx_lock(&ktrace_mtx);
if (p->p_tracevp == vp)
ktr_freeproc(p, &cred, NULL);
mtx_unlock(&ktrace_mtx);
PROC_UNLOCK(p);
if (cred != NULL) {
crfree(cred);
cred = NULL;
}
sx_sunlock(&allproc_lock);
while (vrele_count-- > 0)
vrele(vp);
vrele(vp);
vrele(vp);
}
/*