crash/0005-diskdump-netdump-fix-segmentation-fault-caused-by-fa.patch

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From db8c030857b4e318728c51c20da687906c109d0d Mon Sep 17 00:00:00 2001
From: HATAYAMA Daisuke <d.hatayama@fujitsu.com>
Date: Tue, 30 May 2023 19:38:34 +0900
Subject: [PATCH 05/30] diskdump/netdump: fix segmentation fault caused by
failure of stopping CPUs
There's no NMI on ARM. Hence, stopping the non-panicking CPUs from the
panicking CPU via IPI can fail easily if interrupts are being masked
in those moment. Moreover, crash_notes are not initialized for such
unstopped CPUs and the corresponding NT_PRSTATUS notes are not
attached to vmcore. However, crash utility never takes it
consideration such uninitialized crash_notes and then ends with
mapping different NT_PRSTATUS to actually unstopped CPUs. This corrupt
mapping can result crash utility into segmentation fault in the
operations where register values in NT_PRSTATUS notes are used.
For example:
crash> bt 1408
PID: 1408 TASK: ffff000003e22200 CPU: 2 COMMAND: "repro"
Segmentation fault (core dumped)
crash> help -D
diskdump_data:
filename: 127.0.0.1-2023-05-26-02:21:27/vmcore-ld1
flags: 46 (KDUMP_CMPRS_LOCAL|ERROR_EXCLUDED|LZO_SUPPORTED)
...snip...
notes_buf: 1815df0
num_vmcoredd_notes: 0
num_prstatus_notes: 5
notes[0]: 1815df0 (NT_PRSTATUS)
si.signo: 0 si.code: 0 si.errno: 0
...snip...
PSTATE: 80400005 FPVALID: 00000000
notes[4]: 1808f10 (NT_PRSTATUS)
Segmentation fault (core dumped)
To fix this issue, let's map NT_PRSTATUS to some CPU only if the
corresponding crash_notes is checked to be initialized.
[ kh: moved existence check for crash_notes out of the loop ]
Signed-off-by: HATAYAMA Daisuke <d.hatayama@fujitsu.com>
Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
---
defs.h | 1 +
diskdump.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
netdump.c | 7 ++++++-
3 files changed, 51 insertions(+), 2 deletions(-)
diff --git a/defs.h b/defs.h
index 7d8bb8ab3de1..6520d2f13f48 100644
--- a/defs.h
+++ b/defs.h
@@ -7118,6 +7118,7 @@ int dumpfile_is_split(void);
void show_split_dumpfiles(void);
void x86_process_elf_notes(void *, unsigned long);
void *diskdump_get_prstatus_percpu(int);
+int have_crash_notes(int cpu);
void map_cpus_to_prstatus_kdump_cmprs(void);
void diskdump_display_regs(int, FILE *);
void process_elf32_notes(void *, ulong);
diff --git a/diskdump.c b/diskdump.c
index 94bca4ded572..2c284ff3f97f 100644
--- a/diskdump.c
+++ b/diskdump.c
@@ -101,12 +101,54 @@ int dumpfile_is_split(void)
return KDUMP_SPLIT();
}
+int have_crash_notes(int cpu)
+{
+ ulong crash_notes, notes_ptr;
+ char *buf, *p;
+ Elf64_Nhdr *note = NULL;
+
+ if (!readmem(symbol_value("crash_notes"), KVADDR, &crash_notes,
+ sizeof(crash_notes), "crash_notes", RETURN_ON_ERROR)) {
+ error(WARNING, "cannot read \"crash_notes\"\n");
+ return FALSE;
+ }
+
+ if ((kt->flags & SMP) && (kt->flags & PER_CPU_OFF))
+ notes_ptr = crash_notes + kt->__per_cpu_offset[cpu];
+ else
+ notes_ptr = crash_notes;
+
+ buf = GETBUF(SIZE(note_buf));
+
+ if (!readmem(notes_ptr, KVADDR, buf,
+ SIZE(note_buf), "note_buf_t", RETURN_ON_ERROR)) {
+ error(WARNING, "cpu %d: cannot read NT_PRSTATUS note\n", cpu);
+ return FALSE;
+ }
+
+ note = (Elf64_Nhdr *)buf;
+ p = buf + sizeof(Elf64_Nhdr);
+
+ if (note->n_type != NT_PRSTATUS) {
+ error(WARNING, "cpu %d: invalid NT_PRSTATUS note (n_type != NT_PRSTATUS)\n", cpu);
+ return FALSE;
+ }
+
+ if (!STRNEQ(p, "CORE")) {
+ error(WARNING, "cpu %d: invalid NT_PRSTATUS note (name != \"CORE\")\n", cpu);
+ return FALSE;
+ }
+
+ return TRUE;
+}
+
void
map_cpus_to_prstatus_kdump_cmprs(void)
{
void **nt_ptr;
int online, i, j, nrcpus;
size_t size;
+ int crash_notes_exists;
if (pc->flags2 & QEMU_MEM_DUMP_COMPRESSED) /* notes exist for all cpus */
goto resize_note_pointers;
@@ -129,9 +171,10 @@ map_cpus_to_prstatus_kdump_cmprs(void)
* Re-populate the array with the notes mapping to online cpus
*/
nrcpus = (kt->kernel_NR_CPUS ? kt->kernel_NR_CPUS : NR_CPUS);
+ crash_notes_exists = kernel_symbol_exists("crash_notes");
for (i = 0, j = 0; i < nrcpus; i++) {
- if (in_cpu_map(ONLINE_MAP, i)) {
+ if (in_cpu_map(ONLINE_MAP, i) && (!crash_notes_exists || have_crash_notes(i))) {
dd->nt_prstatus_percpu[i] = nt_ptr[j++];
dd->num_prstatus_notes =
MAX(dd->num_prstatus_notes, i+1);
diff --git a/netdump.c b/netdump.c
index 4eba66cecb55..61ddeaa08831 100644
--- a/netdump.c
+++ b/netdump.c
@@ -75,6 +75,7 @@ map_cpus_to_prstatus(void)
void **nt_ptr;
int online, i, j, nrcpus;
size_t size;
+ int crash_notes_exists;
if (pc->flags2 & QEMU_MEM_DUMP_ELF) /* notes exist for all cpus */
return;
@@ -97,10 +98,14 @@ map_cpus_to_prstatus(void)
* Re-populate the array with the notes mapping to online cpus
*/
nrcpus = (kt->kernel_NR_CPUS ? kt->kernel_NR_CPUS : NR_CPUS);
+ crash_notes_exists = kernel_symbol_exists("crash_notes");
for (i = 0, j = 0; i < nrcpus; i++) {
- if (in_cpu_map(ONLINE_MAP, i))
+ if (in_cpu_map(ONLINE_MAP, i) && (!crash_notes_exists || have_crash_notes(i))) {
nd->nt_prstatus_percpu[i] = nt_ptr[j++];
+ nd->num_prstatus_notes =
+ MAX(nd->num_prstatus_notes, i+1);
+ }
}
FREEBUF(nt_ptr);
--
2.37.1