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core(5): overwrite the oldest core dump

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The '%I' format in the kern.corefile sysctl limits the number of
core files that a process can generate to the number stored in the
debug.ncores sysctl. The '%I' format is replaced by the single digit
index. Previously, if all indexes were taken the kernel would overwrite
only a core file with the highest index in a filename.
Currently the system will create a new core file if there is a free
index or if all slots are taken it will overwrite the oldest one.

Reviewed by:	kib(code), bcr (updating)
Differential Revision:	https://reviews.freebsd.org/D15991
Differential Revision:	https://reviews.freebsd.org/D16084
This commit is contained in:
Mariusz Zaborski 2018-07-01 17:28:46 +00:00
parent 775c9076c7
commit 0dea6e3c98
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=335844
2 changed files with 112 additions and 34 deletions
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8
UPDATING
View File

@ -31,6 +31,14 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 12.x IS SLOW:
disable the most expensive debugging functionality run
"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
20180701:
The '%I' format in the kern.corefile sysctl limits the number of
core files that a process can generate to the number stored in the
debug.ncores sysctl. The '%I' format is replaced by the single digit
index. Previously, if all indexes were taken the kernel would overwrite
only a core file with the highest index in a filename.
Currently the system will create a new core file if there is a free
index or if all slots are taken it will overwrite the oldest one.
20180630:
Clang, llvm, lld, lldb, compiler-rt and libc++ have been upgraded to

138
sys/kern/kern_sig.c
View File

@ -3299,6 +3299,88 @@ SYSCTL_PROC(_kern, OID_AUTO, corefile, CTLTYPE_STRING | CTLFLAG_RW |
CTLFLAG_MPSAFE, 0, 0, sysctl_kern_corefile, "A",
"Process corefile name format string");
static void
vnode_close_locked(struct thread *td, struct vnode *vp)
{
VOP_UNLOCK(vp, 0);
vn_close(vp, FWRITE, td->td_ucred, td);
}
/*
* If the core format has a %I in it, then we need to check
* for existing corefiles before defining a name.
* To do this we iterate over 0..num_cores to find a
* non-existing core file name to use. If all core files are
* already used we choose the oldest one.
*/
static int
corefile_open_last(struct thread *td, char *name, int indexpos,
struct vnode **vpp)
{
struct vnode *oldvp, *nextvp, *vp;
struct vattr vattr;
struct nameidata nd;
int error, i, flags, oflags, cmode;
struct timespec lasttime;
nextvp = oldvp = NULL;
cmode = S_IRUSR | S_IWUSR;
oflags = VN_OPEN_NOAUDIT | VN_OPEN_NAMECACHE |
(capmode_coredump ? VN_OPEN_NOCAPCHECK : 0);
for (i = 0; i < num_cores; i++) {
flags = O_CREAT | FWRITE | O_NOFOLLOW;
name[indexpos] = '0' + i;
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, td);
error = vn_open_cred(&nd, &flags, cmode, oflags, td->td_ucred,
NULL);
if (error != 0)
break;
vp = nd.ni_vp;
NDFREE(&nd, NDF_ONLY_PNBUF);
if ((flags & O_CREAT) == O_CREAT) {
nextvp = vp;
break;
}
error = VOP_GETATTR(vp, &vattr, td->td_ucred);
if (error != 0) {
vnode_close_locked(td, vp);
break;
}
if (oldvp == NULL ||
lasttime.tv_sec > vattr.va_mtime.tv_sec ||
(lasttime.tv_sec == vattr.va_mtime.tv_sec &&
lasttime.tv_nsec >= vattr.va_mtime.tv_nsec)) {
if (oldvp != NULL)
vnode_close_locked(td, oldvp);
oldvp = vp;
lasttime = vattr.va_mtime;
} else {
vnode_close_locked(td, vp);
}
}
if (oldvp != NULL) {
if (nextvp == NULL)
nextvp = oldvp;
else
vnode_close_locked(td, oldvp);
}
if (error != 0) {
if (nextvp != NULL)
vnode_close_locked(td, oldvp);
} else {
*vpp = nextvp;
}
return (error);
}
/*
* corefile_open(comm, uid, pid, td, compress, vpp, namep)
* Expand the name described in corefilename, using name, uid, and pid
@ -3315,11 +3397,11 @@ static int
corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
int compress, struct vnode **vpp, char **namep)
{
struct nameidata nd;
struct sbuf sb;
struct nameidata nd;
const char *format;
char *hostname, *name;
int indexpos, i, error, cmode, flags, oflags;
int cmode, error, flags, i, indexpos, oflags;
hostname = NULL;
format = corefilename;
@ -3385,48 +3467,36 @@ corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
sbuf_finish(&sb);
sbuf_delete(&sb);
cmode = S_IRUSR | S_IWUSR;
oflags = VN_OPEN_NOAUDIT | VN_OPEN_NAMECACHE |
(capmode_coredump ? VN_OPEN_NOCAPCHECK : 0);
/*
* If the core format has a %I in it, then we need to check
* for existing corefiles before returning a name.
* To do this we iterate over 0..num_cores to find a
* non-existing core file name to use.
*/
if (indexpos != -1) {
for (i = 0; i < num_cores; i++) {
flags = O_CREAT | O_EXCL | FWRITE | O_NOFOLLOW;
name[indexpos] = '0' + i;
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, td);
error = vn_open_cred(&nd, &flags, cmode, oflags,
td->td_ucred, NULL);
if (error) {
if (error == EEXIST)
continue;
log(LOG_ERR,
"pid %d (%s), uid (%u): Path `%s' failed "
"on initial open test, error = %d\n",
pid, comm, uid, name, error);
}
goto out;
error = corefile_open_last(td, name, indexpos, vpp);
if (error != 0) {
log(LOG_ERR,
"pid %d (%s), uid (%u): Path `%s' failed "
"on initial open test, error = %d\n",
pid, comm, uid, name, error);
}
} else {
cmode = S_IRUSR | S_IWUSR;
oflags = VN_OPEN_NOAUDIT | VN_OPEN_NAMECACHE |
(capmode_coredump ? VN_OPEN_NOCAPCHECK : 0);
flags = O_CREAT | FWRITE | O_NOFOLLOW;
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, td);
error = vn_open_cred(&nd, &flags, cmode, oflags, td->td_ucred,
NULL);
if (error == 0) {
*vpp = nd.ni_vp;
NDFREE(&nd, NDF_ONLY_PNBUF);
}
}
flags = O_CREAT | FWRITE | O_NOFOLLOW;
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, td);
error = vn_open_cred(&nd, &flags, cmode, oflags, td->td_ucred, NULL);
out:
if (error) {
if (error != 0) {
#ifdef AUDIT
audit_proc_coredump(td, name, error);
#endif
free(name, M_TEMP);
return (error);
}
NDFREE(&nd, NDF_ONLY_PNBUF);
*vpp = nd.ni_vp;
*namep = name;
return (0);
}