[dm-devel] [PATCH] Re: your dm patch for strace
Eugene Syromyatnikov
evgsyr at gmail.com
Sat Oct 8 17:45:46 UTC 2016
Hello.
While digging through your patch, looks like I've stumbled upon what
looks like some minor out-of-bunds write in dm ioctl code: nl->dev = 0
write (drivers/md/dm-ioctl.c:533 @ b66484cd7) could be out of bounds
in case userspace provided data_size of sizeof(struct dm_ioctl) and
there are no device mapper devices present. Since data_size remains
the same, this write does not make it to user space, and since this
memory is kmalloc'ed, it's unlikely it overwrites any data since
struct dm_ioctl size is not divisible by 32, but nevertheless.
On Sun, Oct 2, 2016 at 9:59 PM, Mikulas Patocka <mpatocka at redhat.com> wrote:
>
>
> On Mon, 12 Sep 2016, Dmitry V. Levin wrote:
>
>> > + tprintf("}");
>> > + if (entering(tcp))
>> > + offset = offset + s->next;
>> > + else
>> > + offset = ioc->data_start + s->next;
>>
>> This code trusts s->next; unfortunately, strace cannot trust syscall
>> arguments, otherwise anything may happen, e.g.
>>
>> $ cat ioctl_dm.c
>> #include <sys/ioctl.h>
>> #include <linux/dm-ioctl.h>
>> int main(void)
>> {
>> struct {
>> struct dm_ioctl ioc;
>> struct dm_target_spec spec;
>> int i;
>> } s = {
>> .spec = { 0 },
>> .ioc = {
>> .version[0] = DM_VERSION_MAJOR,
>> .data_size = sizeof(s),
>> .data_start = sizeof(s.ioc),
>> .target_count = -1U
>> }
>> };
>> return !ioctl(-1, DM_TABLE_LOAD, &s);
>> }
>> $ strace -veioctl ./ioctl_dm
>>
>> btw, this parser lacks tests. How one can easily verify that it works
>> correctly? For example how a test for strace ioctl parser may look like
>> see tests/ioctl_* files.
>>
>>
>> --
>> ldv
>
> Here I'm sending new patch. It fixes the possible loop with s->next and
> adds tests:
>
> Makefile.am | 1
> configure.ac | 1
> defs.h | 1
> dm.c | 356 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> ioctl.c | 4
> tests/Makefile.am | 2
> tests/ioctl_dm.c | 78 +++++++++++
> tests/ioctl_dm.test | 12 +
> xlat/dm_flags.in | 17 ++
> 9 files changed, 472 insertions(+)
>
> Index: strace/Makefile.am
> ===================================================================
> --- strace.orig/Makefile.am
> +++ strace/Makefile.am
> @@ -97,6 +97,7 @@ strace_SOURCES = \
> desc.c \
> dirent.c \
> dirent64.c \
> + dm.c \
> empty.h \
> epoll.c \
> evdev.c \
> Index: strace/configure.ac
> ===================================================================
> --- strace.orig/configure.ac
> +++ strace/configure.ac
> @@ -354,6 +354,7 @@ AC_CHECK_HEADERS(m4_normalize([
> elf.h
> inttypes.h
> linux/bsg.h
> + linux/dm-ioctl.h
> linux/dqblk_xfs.h
> linux/falloc.h
> linux/fiemap.h
> Index: strace/defs.h
> ===================================================================
> --- strace.orig/defs.h
> +++ strace/defs.h
> @@ -640,6 +640,7 @@ extern void print_struct_statfs64(struct
>
> extern void print_ifindex(unsigned int);
>
> +extern int dm_ioctl(struct tcb *, const unsigned int, long);
> extern int file_ioctl(struct tcb *, const unsigned int, long);
> extern int fs_x_ioctl(struct tcb *, const unsigned int, long);
> extern int loop_ioctl(struct tcb *, const unsigned int, long);
> Index: strace/dm.c
> ===================================================================
> --- /dev/null
> +++ strace/dm.c
> @@ -0,0 +1,356 @@
> +#include "defs.h"
> +
> +#ifdef HAVE_LINUX_DM_IOCTL_H
> +
> +#include <sys/ioctl.h>
> +#include <linux/dm-ioctl.h>
> +
> +static void
> +dm_decode_device(const unsigned int code, const struct dm_ioctl *ioc)
> +{
> + switch (code) {
> + case DM_REMOVE_ALL:
> + case DM_LIST_DEVICES:
> + case DM_LIST_VERSIONS:
> + break;
> + default:
> + if (ioc->dev)
> + tprintf(", dev=makedev(%u, %u)",
> + major(ioc->dev), minor(ioc->dev));
> + if (ioc->name[0]) {
> + tprints(", name=");
> + print_quoted_string(ioc->name, DM_NAME_LEN,
> + QUOTE_0_TERMINATED);
> + }
> + if (ioc->uuid[0]) {
> + tprints(", uuid=");
> + print_quoted_string(ioc->uuid, DM_UUID_LEN,
> + QUOTE_0_TERMINATED);
> + }
> + break;
> + }
> +}
> +
> +static void
> +dm_decode_values(struct tcb *tcp, const unsigned int code,
> + const struct dm_ioctl *ioc)
> +{
> + if (entering(tcp)) {
> + switch (code) {
> + case DM_TABLE_LOAD:
> + tprintf(", target_count=%"PRIu32"",
> + ioc->target_count);
> + break;
> + case DM_DEV_SUSPEND:
> + if (ioc->flags & DM_SUSPEND_FLAG)
> + break;
> + case DM_DEV_RENAME:
> + case DM_DEV_REMOVE:
> + case DM_DEV_WAIT:
> + tprintf(", event_nr=%"PRIu32"",
> + ioc->event_nr);
> + break;
> + }
> + } else if (!syserror(tcp)) {
> + switch (code) {
> + case DM_DEV_CREATE:
> + case DM_DEV_RENAME:
> + case DM_DEV_SUSPEND:
> + case DM_DEV_STATUS:
> + case DM_DEV_WAIT:
> + case DM_TABLE_LOAD:
> + case DM_TABLE_CLEAR:
> + case DM_TABLE_DEPS:
> + case DM_TABLE_STATUS:
> + case DM_TARGET_MSG:
> + tprintf(", target_count=%"PRIu32"",
> + ioc->target_count);
> + tprintf(", open_count=%"PRIu32"",
> + ioc->open_count);
> + tprintf(", event_nr=%"PRIu32"",
> + ioc->event_nr);
> + break;
> + }
> + }
> +}
> +
> +#include "xlat/dm_flags.h"
> +
> +static void
> +dm_decode_flags(const struct dm_ioctl *ioc)
> +{
> + tprints(", flags=");
> + printflags(dm_flags, ioc->flags, "DM_???");
> +}
> +
> +static void
> +dm_decode_dm_target_spec(struct tcb *tcp, const struct dm_ioctl *ioc,
> + const char *extra, uint32_t extra_size)
> +{
> + uint32_t i;
> + uint32_t offset = ioc->data_start;
> + for (i = 0; i < ioc->target_count; i++) {
> + if (offset + (uint32_t)sizeof(struct dm_target_spec) >= offset &&
> + offset + (uint32_t)sizeof(struct dm_target_spec) < extra_size) {
> + uint32_t new_offset;
> + const struct dm_target_spec *s =
> + (const struct dm_target_spec *)(extra + offset);
> + tprintf(", {sector_start=%"PRIu64", length=%"PRIu64"",
> + (uint64_t)s->sector_start, (uint64_t)s->length);
> + if (!entering(tcp))
> + tprintf(", status=%"PRId32"", s->status);
> + tprints(", target_type=");
> + print_quoted_string(s->target_type, DM_MAX_TYPE_NAME,
> + QUOTE_0_TERMINATED);
> + tprints(", string=");
> + print_quoted_string((const char *)(s + 1), extra_size -
> + (offset +
> + sizeof(struct dm_target_spec)),
> + QUOTE_0_TERMINATED);
> + tprintf("}");
> + if (entering(tcp))
> + new_offset = offset + s->next;
> + else
> + new_offset = ioc->data_start + s->next;
> + if (new_offset <= offset + (uint32_t)sizeof(struct dm_target_spec))
> + goto misplaced;
> + offset = new_offset;
> + } else {
> +misplaced:
> + tprints(", misplaced struct dm_target_spec");
> + break;
> + }
> + }
> +}
> +
> +static void
> +dm_decode_dm_target_deps(const struct dm_ioctl *ioc, const char *extra,
> + uint32_t extra_size)
> +{
> + uint32_t offset = ioc->data_start;
> + if (offset + (uint32_t)offsetof(struct dm_target_deps, dev) >= offset &&
> + offset + (uint32_t)offsetof(struct dm_target_deps, dev) <= extra_size) {
> + uint32_t i;
> + uint32_t space = (extra_size - (offset +
> + offsetof(struct dm_target_deps, dev))) / sizeof(__u64);
> + const struct dm_target_deps *s =
> + (const struct dm_target_deps *)(extra + offset);
> + if (s->count > space)
> + goto misplaced;
> + tprints(", deps={");
> + for (i = 0; i < s->count; i++) {
> + tprintf("%smakedev(%u, %u)", i ? ", " : "",
> + major(s->dev[i]), minor(s->dev[i]));
> + }
> + tprints("}");
> + } else {
> + misplaced:
> + tprints(", misplaced struct dm_target_deps");
> + }
> +}
> +
> +static void
> +dm_decode_dm_name_list(const struct dm_ioctl *ioc, const char *extra,
> + uint32_t extra_size)
> +{
> + uint32_t offset = ioc->data_start;
> + while (1) {
> + if (offset + (uint32_t)offsetof(struct dm_name_list, name) >= offset &&
> + offset + (uint32_t)offsetof(struct dm_name_list, name) < extra_size) {
> + const struct dm_name_list *s =
> + (const struct dm_name_list *)(extra + offset);
> + if (!s->dev)
> + break;
> + tprintf(", {dev=makedev(%u, %u), name=", major(s->dev), minor(s->dev));
> + print_quoted_string(s->name, extra_size - (offset +
> + offsetof(struct dm_name_list,
> + name)), QUOTE_0_TERMINATED);
> + tprints("}");
> + if (!s->next)
> + break;
> + if (offset + s->next <= offset + (uint32_t)offsetof(struct dm_name_list, name))
> + goto misplaced;
> + offset = offset + s->next;
> + } else {
> + misplaced:
> + tprints(", misplaced struct dm_name_list");
> + break;
> + }
> + }
> +}
> +
> +static void
> +dm_decode_dm_target_versions(const struct dm_ioctl *ioc, const char *extra,
> + uint32_t extra_size)
> +{
> + uint32_t offset = ioc->data_start;
> + while (1) {
> + if (offset + (uint32_t)offsetof(struct dm_target_versions, name) >=
> + offset &&
> + offset + (uint32_t)offsetof(struct dm_target_versions, name) <
> + extra_size) {
> + const struct dm_target_versions *s =
> + (const struct dm_target_versions *)(extra + offset);
> + tprints(", {name=");
> + print_quoted_string(s->name, extra_size - (offset +
> + offsetof(struct dm_target_versions,
> + name)), QUOTE_0_TERMINATED);
> + tprintf(", version=%"PRIu32".%"PRIu32".%"PRIu32"}",
> + s->version[0], s->version[1], s->version[2]);
> + if (!s->next)
> + break;
> + if (offset + s->next <= offset + (uint32_t)offsetof(struct dm_target_versions, name))
> + goto misplaced;
> + offset = offset + s->next;
> + } else {
> + misplaced:
> + tprints(", misplaced struct dm_target_versions");
> + break;
> + }
> + }
> +}
> +
> +static void
> +dm_decode_dm_target_msg(const struct dm_ioctl *ioc, const char *extra,
> + uint32_t extra_size)
> +{
> + uint32_t offset = ioc->data_start;
> + if (offset + (uint32_t)offsetof(struct dm_target_msg, message) >= offset &&
> + offset + (uint32_t)offsetof(struct dm_target_msg, message) < extra_size) {
> + const struct dm_target_msg *s =
> + (const struct dm_target_msg *)(extra + offset);
> + tprintf(", {sector=%"PRIu64", message=", (uint64_t)s->sector);
> + print_quoted_string(s->message, extra_size -
> + offsetof(struct dm_target_msg, message),
> + QUOTE_0_TERMINATED);
> + tprints("}");
> + } else {
> + tprints(", misplaced struct dm_target_msg");
> + }
> +}
> +
> +static void
> +dm_decode_string(const struct dm_ioctl *ioc, const char *extra,
> + uint32_t extra_size)
> +{
> + uint32_t offset = ioc->data_start;
> + if (offset < extra_size) {
> + tprints(", string=");
> + print_quoted_string(extra + offset, extra_size - offset,
> + QUOTE_0_TERMINATED);
> + } else {
> + tprints(", misplaced string");
> + }
> +}
> +
> +static int
> +dm_known_ioctl(struct tcb *tcp, const unsigned int code, long arg)
> +{
> + struct dm_ioctl ioc;
> + char *extra = NULL;
> + uint32_t extra_size = 0;
> +
> + if (umoven(tcp, arg, sizeof(ioc) - sizeof(ioc.data), (char *)&ioc) < 0)
> + return 0;
> + tprintf(", {version=%d.%d.%d", ioc.version[0], ioc.version[1],
> + ioc.version[2]);
> +
> + /*
> + * if we use a different version of ABI, do not attempt to decode
> + * ioctl fields
> + */
> + if (ioc.version[0] != DM_VERSION_MAJOR)
> + goto skip;
> +
> + if (ioc.data_size > sizeof(ioc)) {
> + extra = malloc(ioc.data_size);
> + if (extra) {
> + extra_size = ioc.data_size;
> + if (umoven(tcp, arg, extra_size, extra) < 0) {
> + free(extra);
> + extra = NULL;
> + extra_size = 0;
> + }
> + }
> + }
> + dm_decode_device(code, &ioc);
> + dm_decode_values(tcp, code, &ioc);
> + dm_decode_flags(&ioc);
> + if (!abbrev(tcp)) switch (code) {
> + case DM_DEV_WAIT:
> + case DM_TABLE_STATUS:
> + if (entering(tcp) || syserror(tcp))
> + break;
> + dm_decode_dm_target_spec(tcp, &ioc, extra, extra_size);
> + break;
> + case DM_TABLE_LOAD:
> + if (!entering(tcp))
> + break;
> + dm_decode_dm_target_spec(tcp, &ioc, extra, extra_size);
> + break;
> + case DM_TABLE_DEPS:
> + if (entering(tcp) || syserror(tcp))
> + break;
> + dm_decode_dm_target_deps(&ioc, extra, extra_size);
> + break;
> + case DM_LIST_DEVICES:
> + if (entering(tcp) || syserror(tcp))
> + break;
> + dm_decode_dm_name_list(&ioc, extra, extra_size);
> + break;
> + case DM_LIST_VERSIONS:
> + if (entering(tcp) || syserror(tcp))
> + break;
> + dm_decode_dm_target_versions(&ioc, extra, extra_size);
> + break;
> + case DM_TARGET_MSG:
> + if (entering(tcp)) {
> + dm_decode_dm_target_msg(&ioc, extra,
> + extra_size);
> + } else if (!syserror(tcp) &&
> + ioc.flags & DM_DATA_OUT_FLAG) {
> + dm_decode_string(&ioc, extra, extra_size);
> + }
> + break;
> + case DM_DEV_RENAME:
> + case DM_DEV_SET_GEOMETRY:
> + if (!entering(tcp))
> + break;
> + dm_decode_string(&ioc, extra, extra_size);
> + break;
> + }
> +
> + skip:
> + tprints("}");
> + if (extra)
> + free(extra);
> + return 1;
> +}
> +
> +int
> +dm_ioctl(struct tcb *tcp, const unsigned int code, long arg)
> +{
> + switch (code) {
> + case DM_VERSION:
> + case DM_REMOVE_ALL:
> + case DM_LIST_DEVICES:
> + case DM_DEV_CREATE:
> + case DM_DEV_REMOVE:
> + case DM_DEV_RENAME:
> + case DM_DEV_SUSPEND:
> + case DM_DEV_STATUS:
> + case DM_DEV_WAIT:
> + case DM_TABLE_LOAD:
> + case DM_TABLE_CLEAR:
> + case DM_TABLE_DEPS:
> + case DM_TABLE_STATUS:
> + case DM_LIST_VERSIONS:
> + case DM_TARGET_MSG:
> + case DM_DEV_SET_GEOMETRY:
> + return dm_known_ioctl(tcp, code, arg);
> + default:
> + return 0;
> + }
> +}
> +
> +#endif
> Index: strace/ioctl.c
> ===================================================================
> --- strace.orig/ioctl.c
> +++ strace/ioctl.c
> @@ -282,6 +282,10 @@ ioctl_decode(struct tcb *tcp)
> case 0x94:
> return btrfs_ioctl(tcp, code, arg);
> #endif
> +#ifdef HAVE_LINUX_DM_IOCTL_H
> + case 0xfd:
> + return dm_ioctl(tcp, code, arg);
> +#endif
> default:
> break;
> }
> Index: strace/tests/Makefile.am
> ===================================================================
> --- strace.orig/tests/Makefile.am
> +++ strace/tests/Makefile.am
> @@ -161,6 +161,7 @@ check_PROGRAMS = \
> inet-cmsg \
> ioctl \
> ioctl_block \
> + ioctl_dm \
> ioctl_evdev \
> ioctl_evdev-v \
> ioctl_mtd \
> @@ -503,6 +504,7 @@ DECODER_TESTS = \
> inet-cmsg.test \
> ioctl.test \
> ioctl_block.test \
> + ioctl_dm.test \
> ioctl_evdev.test \
> ioctl_evdev-v.test \
> ioctl_mtd.test \
> Index: strace/tests/ioctl_dm.c
> ===================================================================
> --- /dev/null
> +++ strace/tests/ioctl_dm.c
> @@ -0,0 +1,78 @@
> +#include "tests.h"
> +#include <stdio.h>
> +#include <stddef.h>
> +#include <string.h>
> +#include <sys/ioctl.h>
> +#include <linux/dm-ioctl.h>
> +
> +static struct s {
> + struct dm_ioctl ioc;
> + union {
> + struct {
> + struct dm_target_spec target_spec;
> + char target_params[256];
> + } ts;
> + struct {
> + struct dm_target_msg target_msg;
> + char target_string[256];
> + } tm;
> + char string[256];
> + } u;
> +} s;
> +
> +static void init_s(void)
> +{
> + memset(&s, 0, sizeof s);
> + s.ioc.version[0] = DM_VERSION_MAJOR;
> + s.ioc.version[1] = 1;
> + s.ioc.version[2] = 2;
> + s.ioc.data_size = sizeof(s);
> + s.ioc.data_start = offsetof(struct s, u);
> + s.ioc.dev = 0x1234;
> + strcpy(s.ioc.name, "nnn");
> + strcpy(s.ioc.uuid, "uuu");
> +}
> +
> +int
> +main(void)
> +{
> + init_s();
> + s.ioc.data_size = sizeof(s.ioc);
> + s.ioc.data_start = 0;
> + ioctl(-1, DM_VERSION, &s);
> + printf("ioctl(-1, DM_VERSION, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", flags=0}, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", flags=0}) = -1 EBADF (%m)\n");
> +
> + init_s();
> + s.ioc.target_count = 1;
> + s.u.ts.target_spec.sector_start = 0x10;
> + s.u.ts.target_spec.length = 0x20;
> + s.u.ts.target_spec.next = sizeof(s.u.ts.target_spec) + sizeof(s.u.ts.target_params);
> + strcpy(s.u.ts.target_spec.target_type, "tgt");
> + strcpy(s.u.ts.target_params, "tparams");
> + ioctl(-1, DM_TABLE_LOAD, &s);
> + printf("ioctl(-1, DM_TABLE_LOAD, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", target_count=1, flags=0, {sector_start=16, length=32, target_type=\"tgt\", string=\"tparams\"}}, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", flags=0}) = -1 EBADF (%m)\n");
> +
> + init_s();
> + s.u.tm.target_msg.sector = 0x1234;
> + strcpy(s.u.tm.target_msg.message, "tmsg");
> + ioctl(-1, DM_TARGET_MSG, &s);
> + printf("ioctl(-1, DM_TARGET_MSG, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", flags=0, {sector=4660, message=\"tmsg\"}}, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", flags=0}) = -1 EBADF (%m)\n");
> +
> + init_s();
> + strcpy(s.u.string, "10 20 30 40");
> + ioctl(-1, DM_DEV_SET_GEOMETRY, &s);
> + printf("ioctl(-1, DM_DEV_SET_GEOMETRY, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", flags=0, string=\"10 20 30 40\"}, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", flags=0}) = -1 EBADF (%m)\n");
> +
> + init_s();
> + strcpy(s.u.string, "new-name");
> + ioctl(-1, DM_DEV_RENAME, &s);
> + printf("ioctl(-1, DM_DEV_RENAME, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", event_nr=0, flags=0, string=\"new-name\"}, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", flags=0}) = -1 EBADF (%m)\n");
> +
> + init_s();
> + s.ioc.target_count = -1U;
> + ioctl(-1, DM_TABLE_LOAD, &s);
> + printf("ioctl(-1, DM_TABLE_LOAD, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", target_count=4294967295, flags=0, {sector_start=0, length=0, target_type=\"\", string=\"\"}, misplaced struct dm_target_spec}, {version=4.1.2, dev=makedev(18, 52), name=\"nnn\", uuid=\"uuu\", flags=0}) = -1 EBADF (%m)\n");
> +
> + puts("+++ exited with 0 +++");
> + return 0;
> +}
> Index: strace/tests/ioctl_dm.test
> ===================================================================
> --- /dev/null
> +++ strace/tests/ioctl_dm.test
> @@ -0,0 +1,12 @@
> +#!/bin/sh
> +
> +# Check decoding of DM* ioctls.
> +
> +. "${srcdir=.}/init.sh"
> +
> +run_prog > /dev/null
> +run_strace -a16 -veioctl $args > "$EXP"
> +check_prog grep
> +grep -v '^ioctl([012],' < "$LOG" > "$OUT"
> +match_diff "$OUT" "$EXP"
> +rm -f "$EXP" "$OUT"
> Index: strace/xlat/dm_flags.in
> ===================================================================
> --- /dev/null
> +++ strace/xlat/dm_flags.in
> @@ -0,0 +1,17 @@
> +DM_READONLY_FLAG
> +DM_SUSPEND_FLAG
> +DM_PERSISTENT_DEV_FLAG
> +DM_STATUS_TABLE_FLAG
> +DM_ACTIVE_PRESENT_FLAG
> +DM_INACTIVE_PRESENT_FLAG
> +DM_BUFFER_FULL_FLAG
> +DM_SKIP_BDGET_FLAG
> +DM_SKIP_LOCKFS_FLAG
> +DM_NOFLUSH_FLAG
> +DM_QUERY_INACTIVE_TABLE_FLAG
> +DM_UEVENT_GENERATED_FLAG
> +DM_UUID_FLAG
> +DM_SECURE_DATA_FLAG
> +DM_DATA_OUT_FLAG
> +DM_DEFERRED_REMOVE
> +DM_INTERNAL_SUSPEND_FLAG
>
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> Strace-devel mailing list
> Strace-devel at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/strace-devel
--
Eugene "eSyr" Syromyatnikov
mailto:evgSyr at gmail.com
xmpp:eSyr at jabber.{ru|org}
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