Thanks for catching this Stefan.
On 1/23/24 19:38, Stefan Berger wrote:
kbuf.buffer = kexec_buffer;
kbuf.bufsz = kexec_buffer_size;
kbuf.memsz = kexec_segment_size;
A dent with this patch when only applying this patch:
Two consecutive kexec loads lead to this here:
[ 30.670330] IMA buffer at 0x3fff10000, size = 0xf0000
[ 32.519618] ------------[ cut here ]------------
[ 32.519669] Trying to vfree() nonexistent vm area (00000000093ae29c)
[ 32.519762] WARNING: CPU: 11 PID: 1796 at mm/vmalloc.c:2826
vfree+0x254/0x340
[ 32.519786] Modules linked in: bonding tls rfkill sunrpc
virtio_console virtio_balloon crct10dif_vpmsum fuse loop zram bochs
drm_vram_helper drm_kms_helper drm_ttm_helper ttm ibmvscsi
scsi_transport_srp drm virtio_blk virtio_net vmx_crypto net_failover
crc32c_vpmsum failover pseries_wdt drm_panel_orientation_quirks
scsi_dh_rdac scsi_dh_emc scsi_dh_alua dm_multipath
[ 32.519939] CPU: 11 PID: 1796 Comm: kexec Not tainted 6.5.0+ #112
[ 32.519953] Hardware name: IBM pSeries (emulated by qemu) POWER8E
(raw) 0x4b0201 0xf000004 of:SLOF,git-5b4c5a hv:linux,kvm pSeries
[ 32.519973] NIP: c0000000004bd004 LR: c0000000004bd000 CTR:
c00000000017ef00
[ 32.519986] REGS: c00000004593b670 TRAP: 0700 Not tainted (6.5.0+)
[ 32.519999] MSR: 8000000002029033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR:
44424842 XER: 00000000
[ 32.520023] CFAR: c0000000001515b0 IRQMASK: 0
GPR00: c0000000004bd000 c00000004593b910
c000000001e17000 0000000000000038
GPR04: 00000000ffffbfff c00000004593b6e8
c00000004593b6e0 00000003f9580000
GPR08: 0000000000000027 c0000003fb707010
0000000000000001 0000000044424842
GPR12: c00000000017ef00 c00000003fff1300
0000000000000000 0000000000000000
GPR16: 0000000000000000 0000000000000000
0000000000000000 0000000000000000
GPR20: 0000000000000000 0000000000000000
0000000000000003 0000000000000004
GPR24: 00007fffeab0f68f 000000000000004c
0000000000000000 c00000002bdce400
GPR28: c000000002bf28f0 0000000000000000
c008000004770000 0000000000000000
[ 32.520180] NIP [c0000000004bd004] vfree+0x254/0x340
[ 32.520212] LR [c0000000004bd000] vfree+0x250/0x340
[ 32.520225] Call Trace:
[ 32.520232] [c00000004593b910] [c0000000004bd000] vfree+0x250/0x340
(unreliable)
[ 32.520250] [c00000004593b990] [c00000000091d590]
ima_add_kexec_buffer+0xe0/0x3c0
[ 32.520296] [c00000004593ba90] [c000000000280968]
sys_kexec_file_load+0x148/0x9b0
[ 32.520333] [c00000004593bb70] [c00000000002ea84]
system_call_exception+0x174/0x320
[ 32.520372] [c00000004593be50] [c00000000000d6a0]
system_call_common+0x160/0x2c4
[ 32.520408] --- interrupt: c00 at 0x7fffa52e7ae4
[ 32.520420] NIP: 00007fffa52e7ae4 LR: 0000000108481d8c CTR:
0000000000000000
[ 32.520452] REGS: c00000004593be80 TRAP: 0c00 Not tainted (6.5.0+)
[ 32.520483] MSR: 800000000000f033 <SF,EE,PR,FP,ME,IR,DR,RI,LE>
CR: 24424202 XER: 00000000
[ 32.520507] IRQMASK: 0
GPR00: 000000000000017e 00007fffeab09470
00007fffa53f6f00 0000000000000003
GPR04: 0000000000000004 000000000000004c
00007fffeab0f68f 0000000000000000
GPR08: 0000000000000000 0000000000000000
0000000000000000 0000000000000000
GPR12: 0000000000000000 00007fffa559b280
0000000000000002 0000000000000001
GPR16: 0000000000000000 0000000000000000
0000000000000000 0000000000000000
GPR20: 00007fffa53f0454 00007fffa53f0458
0000000000000000 0000000000000001
GPR24: 0000000000000000 00007fffeab0f64d
0000000000000006 0000000000000000
GPR28: 0000000000000003 00007fffeab09530
00007fffeab09b08 0000000000000007
[ 32.520767] NIP [00007fffa52e7ae4] 0x7fffa52e7ae4
[ 32.521192] LR [0000000108481d8c] 0x108481d8c
[ 32.521587] --- interrupt: c00
[ 32.521981] Code: 3884c208 4bfc20f1 60000000 0fe00000 60000000
60000000 60420000 3c62ff94 7fc4f378 38632b20 4bc944cd 60000000
<0fe00000> eba10068 4bffff34 2c080000
[ 32.522823] ---[ end trace 0000000000000000 ]---
[ 32.536347] Removed old IMA buffer reservation.
[ 32.536473] IMA buffer at 0x3fff10000, size = 0xf0000
This vfree here probably has to go:
ret = kexec_add_buffer(&kbuf);
if (ret) {
pr_err("Error passing over kexec measurement
buffer.\n");
vfree(kexec_buffer);
return;
}
The vfree may need to be removed or replaced with
ima_free_kexec_file_buf() but it doesn't seem to solve the problem alone.
I got rid of this issue later with this:
static void ima_reset_kexec_file(struct seq_file *sf)
{
sf->buf = NULL;
sf->size = 0;
sf->read_pos = 0;
sf->count = 0;
}
static void ima_free_kexec_file_buf(struct seq_file *sf)
{
vfree(sf->buf);
ima_reset_kexec_file(sf);
}
[...]
I was able to repro the issue by calling kexec 'load' multiple times on
patch #1. Good catch, thanks.
Earlier I was testing the multiple 'load' scenario on the last patch only.
Here onward I will call it on each of the patch individually.
@@ -170,6 +175,9 @@ void ima_add_kexec_buffer(struct kimage *image)
image->ima_segment_index = image->nr_segments - 1;
image->is_ima_segment_index_set = true;
+ /* kexec owns kexec_buffer since kexec_add_buffer and will
vfree() it */
+ ima_reset_kexec_file(&ima_kexec_file);
+
pr_debug("kexec measurement buffer for the loaded kernel at
0x%lx.\n",
kbuf.mem);
Thanks for the suggested solution. Looks like you applied it on top of
patch #3.
I applied it on patch #1, and it seems to be working.
I will dig deeper to ensure it doesn't cause any memory leaks, and will
incorporate it in v5.
Thanks again.
~Tushar
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