[PATCH v4 1/7] ima: define and call ima_alloc_kexec_file_buf
Stefan Berger
stefanb at linux.ibm.com
Tue Jan 23 18:54:30 PST 2024
On 1/22/24 13:37, Tushar Sugandhi wrote:
> Refactor ima_dump_measurement_list() to move the memory allocation part
> to a separate function ima_alloc_kexec_file_buf() which allocates buffer
> of size 'kexec_segment_size' at kexec 'load'. Make the local variable
> ima_kexec_file in function ima_dump_measurement_list() as local static to
> the file, so that it can be accessed from ima_alloc_kexec_file_buf().
> Make necessary changes to the function ima_add_kexec_buffer() to call the
> above two functions.
>
> Signed-off-by: Tushar Sugandhi <tusharsu at linux.microsoft.com>
> ---
> security/integrity/ima/ima_kexec.c | 96 +++++++++++++++++++++---------
> 1 file changed, 67 insertions(+), 29 deletions(-)
>
> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> index 419dc405c831..99daac355c70 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -15,62 +15,93 @@
> #include "ima.h"
>
> #ifdef CONFIG_IMA_KEXEC
> +static struct seq_file ima_kexec_file;
> +
> +static void ima_free_kexec_file_buf(struct seq_file *sf)
> +{
> + vfree(sf->buf);
> + sf->buf = NULL;
> + sf->size = 0;
> + sf->read_pos = 0;
> + sf->count = 0;
> +}
> +
> +static int ima_alloc_kexec_file_buf(size_t segment_size)
> +{
> + /*
> + * kexec 'load' may be called multiple times.
> + * Free and realloc the buffer only if the segment_size is
> + * changed from the previous kexec 'load' call.
> + */
> + if (ima_kexec_file.buf &&
> + ima_kexec_file.size == segment_size &&
> + ima_kexec_file.read_pos == 0 &&
> + ima_kexec_file.count == sizeof(struct ima_kexec_hdr))
> + return 0;
> +
> + ima_free_kexec_file_buf(&ima_kexec_file);
> +
> + /* segment size can't change between kexec load and execute */
> + ima_kexec_file.buf = vmalloc(segment_size);
> + if (!ima_kexec_file.buf)
> + return -ENOMEM;
> +
> + ima_kexec_file.size = segment_size;
> + ima_kexec_file.read_pos = 0;
> + ima_kexec_file.count = sizeof(struct ima_kexec_hdr); /* reserved space */
> +
> + return 0;
> +}
> +
> static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
> unsigned long segment_size)
> {
> struct ima_queue_entry *qe;
> - struct seq_file file;
> struct ima_kexec_hdr khdr;
> - int ret = 0;
>
> - /* segment size can't change between kexec load and execute */
> - file.buf = vmalloc(segment_size);
> - if (!file.buf) {
> - ret = -ENOMEM;
> - goto out;
> + if (!ima_kexec_file.buf) {
> + *buffer_size = 0;
> + *buffer = NULL;
> + pr_err("%s: Kexec file buf not allocated\n", __func__);
> + return -EINVAL;
> }
>
> - file.size = segment_size;
> - file.read_pos = 0;
> - file.count = sizeof(khdr); /* reserved space */
> -
> memset(&khdr, 0, sizeof(khdr));
> khdr.version = 1;
> +
> + /* Copy as many IMA measurements list records as possible */
> list_for_each_entry_rcu(qe, &ima_measurements, later) {
> - if (file.count < file.size) {
> + if (ima_kexec_file.count < ima_kexec_file.size) {
> khdr.count++;
> - ima_measurements_show(&file, qe);
> + ima_measurements_show(&ima_kexec_file, qe);
> } else {
> - ret = -EINVAL;
> + pr_err("%s: IMA log file is too big for Kexec buf\n",
> + __func__);
> break;
> }
> }
>
> - if (ret < 0)
> - goto out;
> -
> /*
> * fill in reserved space with some buffer details
> * (eg. version, buffer size, number of measurements)
> */
> - khdr.buffer_size = file.count;
> + khdr.buffer_size = ima_kexec_file.count;
> if (ima_canonical_fmt) {
> khdr.version = cpu_to_le16(khdr.version);
> khdr.count = cpu_to_le64(khdr.count);
> khdr.buffer_size = cpu_to_le64(khdr.buffer_size);
> }
> - memcpy(file.buf, &khdr, sizeof(khdr));
> + memcpy(ima_kexec_file.buf, &khdr, sizeof(khdr));
>
> print_hex_dump_debug("ima dump: ", DUMP_PREFIX_NONE, 16, 1,
> - file.buf, file.count < 100 ? file.count : 100,
> + ima_kexec_file.buf, ima_kexec_file.count < 100 ?
> + ima_kexec_file.count : 100,
> true);
>
> - *buffer_size = file.count;
> - *buffer = file.buf;
> -out:
> - if (ret == -EINVAL)
> - vfree(file.buf);
> - return ret;
> + *buffer_size = ima_kexec_file.count;
> + *buffer = ima_kexec_file.buf;
> +
> + return 0;
> }
>
> /*
> @@ -108,13 +139,20 @@ void ima_add_kexec_buffer(struct kimage *image)
> return;
> }
>
> - ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer,
> - kexec_segment_size);
> - if (!kexec_buffer) {
> + ret = ima_alloc_kexec_file_buf(kexec_segment_size);
> + if (ret < 0) {
> pr_err("Not enough memory for the kexec measurement buffer.\n");
> return;
> }
>
> + ret = ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer,
> + kexec_segment_size);
> + if (ret < 0) {
> + pr_err("%s: Failed to dump IMA measurements. Error:%d.\n",
> + __func__, ret);
> + return;
> + }
> +
> 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;
}
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