e6b95927f3
This fix is spiritually similar to r287442 and was discovered thanks to the KASSERT added in that revision. NT_PROCSTAT_VMMAP output length, when packing kinfo structs, is tied to the length of filenames corresponding to vnodes in the process' vm map via vn_fullpath. As vnodes may move during coredump, this is racy. We do not remove the race, only prevent it from causing coredump corruption. - Add a sysctl, kern.coredump_pack_vmmapinfo, to allow users to disable kinfo packing for PROCSTAT_VMMAP notes. This avoids VMMAP corruption and truncation, even if names change, at the cost of up to PATH_MAX bytes per mapped object. The new sysctl is documented in core.5. - Fix note_procstat_vmmap to self-limit in the second pass. This addresses corruption, at the cost of sometimes producing a truncated result. - Fix PROCSTAT_VMMAP consumers libutil (and libprocstat, via copy-paste) to grok the new zero padding. Reported by: pho (https://people.freebsd.org/~pho/stress/log/datamove4-2.txt) Relnotes: yes Sponsored by: EMC / Isilon Storage Division Differential Revision: https://reviews.freebsd.org/D3824
78 lines
1.5 KiB
C
78 lines
1.5 KiB
C
#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/user.h>
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#include <sys/sysctl.h>
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#include <stdlib.h>
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#include <string.h>
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#include "libutil.h"
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struct kinfo_vmentry *
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kinfo_getvmmap(pid_t pid, int *cntp)
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{
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int mib[4];
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int error;
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int cnt;
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size_t len;
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char *buf, *bp, *eb;
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struct kinfo_vmentry *kiv, *kp, *kv;
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*cntp = 0;
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len = 0;
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mib[0] = CTL_KERN;
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mib[1] = KERN_PROC;
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mib[2] = KERN_PROC_VMMAP;
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mib[3] = pid;
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error = sysctl(mib, 4, NULL, &len, NULL, 0);
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if (error)
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return (NULL);
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len = len * 4 / 3;
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buf = malloc(len);
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if (buf == NULL)
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return (NULL);
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error = sysctl(mib, 4, buf, &len, NULL, 0);
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if (error) {
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free(buf);
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return (NULL);
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}
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/* Pass 1: count items */
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cnt = 0;
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bp = buf;
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eb = buf + len;
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while (bp < eb) {
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kv = (struct kinfo_vmentry *)(uintptr_t)bp;
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if (kv->kve_structsize == 0)
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break;
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bp += kv->kve_structsize;
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cnt++;
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}
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kiv = calloc(cnt, sizeof(*kiv));
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if (kiv == NULL) {
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free(buf);
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return (NULL);
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}
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bp = buf;
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eb = buf + len;
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kp = kiv;
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/* Pass 2: unpack */
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while (bp < eb) {
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kv = (struct kinfo_vmentry *)(uintptr_t)bp;
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if (kv->kve_structsize == 0)
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break;
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/* Copy/expand into pre-zeroed buffer */
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memcpy(kp, kv, kv->kve_structsize);
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/* Advance to next packed record */
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bp += kv->kve_structsize;
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/* Set field size to fixed length, advance */
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kp->kve_structsize = sizeof(*kp);
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kp++;
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}
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free(buf);
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*cntp = cnt;
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return (kiv); /* Caller must free() return value */
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}
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