14bdbaf2e4
Coredump notes depend on being able to invoke dump routines twice; once in a dry-run mode to get the size of the note, and another to actually emit the note to the corefile. When a note helper emits a different length section the second time around than the length it requested the first time, the kernel produces a corrupt coredump. NT_PROCSTAT_FILES output length, when packing kinfo structs, is tied to the length of filenames corresponding to vnodes in the process' fd table via vn_fullpath. As vnodes may move around during dump, this is racy. So: - Detect badly behaved notes in putnote() and pad underfilled notes. - Add a fail point, debug.fail_point.fill_kinfo_vnode__random_path to exercise the NT_PROCSTAT_FILES corruption. It simply picks random lengths to expand or truncate paths to in fo_fill_kinfo_vnode(). - Add a sysctl, kern.coredump_pack_fileinfo, to allow users to disable kinfo packing for PROCSTAT_FILES notes. This should avoid both FILES note corruption and truncation, even if filenames change, at the cost of about 1 kiB in padding bloat per open fd. Document the new sysctl in core.5. - Fix note_procstat_files to self-limit in the 2nd pass. Since sometimes this will result in a short write, pad up to our advertised size. This addresses note corruption, at the risk of sometimes truncating the last several fd info entries. - Fix NT_PROCSTAT_FILES consumers libutil and libprocstat to grok the zero padding. With suggestions from: bjk, jhb, kib, wblock Approved by: markj (mentor) Relnotes: yes Sponsored by: EMC / Isilon Storage Division Differential Revision: https://reviews.freebsd.org/D3548
78 lines
1.4 KiB
C
78 lines
1.4 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_file *
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kinfo_getfile(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_file *kif, *kp, *kf;
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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_FILEDESC;
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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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kf = (struct kinfo_file *)(uintptr_t)bp;
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if (kf->kf_structsize == 0)
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break;
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bp += kf->kf_structsize;
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cnt++;
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}
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kif = calloc(cnt, sizeof(*kif));
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if (kif == 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 = kif;
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/* Pass 2: unpack */
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while (bp < eb) {
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kf = (struct kinfo_file *)(uintptr_t)bp;
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if (kf->kf_structsize == 0)
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break;
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/* Copy/expand into pre-zeroed buffer */
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memcpy(kp, kf, kf->kf_structsize);
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/* Advance to next packed record */
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bp += kf->kf_structsize;
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/* Set field size to fixed length, advance */
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kp->kf_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 (kif); /* Caller must free() return value */
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}
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