From: Julien Grall <julien@xen.org>
To: xen-devel@lists.xenproject.org
Cc: julien@xen.org, Julien Grall <jgrall@amazon.com>,
Ian Jackson <iwj@xenproject.org>, Wei Liu <wl@xen.org>,
Juergen Gross <jgross@suse.com>
Subject: [PATCH] tools/xenstored: Prevent a buffer overflow in dump_state_node_perms()
Date: Thu, 6 May 2021 17:12:23 +0100 [thread overview]
Message-ID: <20210506161223.15984-1-julien@xen.org> (raw)
From: Julien Grall <jgrall@amazon.com>
ASAN reported one issue when Live Updating Xenstored:
=================================================================
==873==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffc194f53e0 at pc 0x555c6b323292 bp 0x7ffc194f5340 sp 0x7ffc194f5338
WRITE of size 1 at 0x7ffc194f53e0 thread T0
#0 0x555c6b323291 in dump_state_node_perms xen/tools/xenstore/xenstored_core.c:2468
#1 0x555c6b32746e in dump_state_special_node xen/tools/xenstore/xenstored_domain.c:1257
#2 0x555c6b32a702 in dump_state_special_nodes xen/tools/xenstore/xenstored_domain.c:1273
#3 0x555c6b32ddb3 in lu_dump_state xen/tools/xenstore/xenstored_control.c:521
#4 0x555c6b32e380 in do_lu_start xen/tools/xenstore/xenstored_control.c:660
#5 0x555c6b31b461 in call_delayed xen/tools/xenstore/xenstored_core.c:278
#6 0x555c6b32275e in main xen/tools/xenstore/xenstored_core.c:2357
#7 0x7f95eecf3d09 in __libc_start_main ../csu/libc-start.c:308
#8 0x555c6b3197e9 in _start (/usr/local/sbin/xenstored+0xc7e9)
Address 0x7ffc194f53e0 is located in stack of thread T0 at offset 80 in frame
#0 0x555c6b32713e in dump_state_special_node xen/tools/xenstore/xenstored_domain.c:1232
This frame has 2 object(s):
[32, 40) 'head' (line 1233)
[64, 80) 'sn' (line 1234) <== Memory access at offset 80 overflows this variable
This is happening because the callers are passing a pointer to a variable
allocated on the stack. However, the field perms is a dynamic array, so
Xenstored will end up to read outside of the variable.
Rework the code so the permissions are written one by one in the fd.
Fixes: ed6eebf17d2c ("tools/xenstore: dump the xenstore state for live update")
Signed-off-by: Julien Grall <jgrall@amazon.com>
---
tools/xenstore/xenstored_core.c | 26 ++++++++++++++------------
tools/xenstore/xenstored_core.h | 3 +--
tools/xenstore/xenstored_domain.c | 2 +-
3 files changed, 16 insertions(+), 15 deletions(-)
diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index d54a6042a9f7..f68da12b5b23 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -2447,34 +2447,36 @@ const char *dump_state_buffered_data(FILE *fp, const struct connection *c,
return NULL;
}
-const char *dump_state_node_perms(FILE *fp, struct xs_state_node *sn,
- const struct xs_permissions *perms,
+const char *dump_state_node_perms(FILE *fp, const struct xs_permissions *perms,
unsigned int n_perms)
{
unsigned int p;
for (p = 0; p < n_perms; p++) {
+ struct xs_state_node_perm sp;
+
switch ((int)perms[p].perms & ~XS_PERM_IGNORE) {
case XS_PERM_READ:
- sn->perms[p].access = XS_STATE_NODE_PERM_READ;
+ sp.access = XS_STATE_NODE_PERM_READ;
break;
case XS_PERM_WRITE:
- sn->perms[p].access = XS_STATE_NODE_PERM_WRITE;
+ sp.access = XS_STATE_NODE_PERM_WRITE;
break;
case XS_PERM_READ | XS_PERM_WRITE:
- sn->perms[p].access = XS_STATE_NODE_PERM_BOTH;
+ sp.access = XS_STATE_NODE_PERM_BOTH;
break;
default:
- sn->perms[p].access = XS_STATE_NODE_PERM_NONE;
+ sp.access = XS_STATE_NODE_PERM_NONE;
break;
}
- sn->perms[p].flags = (perms[p].perms & XS_PERM_IGNORE)
+ sp.flags = (perms[p].perms & XS_PERM_IGNORE)
? XS_STATE_NODE_PERM_IGNORE : 0;
- sn->perms[p].domid = perms[p].id;
- }
+ sp.domid = perms[p].id;
- if (fwrite(sn->perms, sizeof(*sn->perms), n_perms, fp) != n_perms)
- return "Dump node permissions error";
+ if (fwrite(&sp, sizeof(sp), 1, fp) != 1)
+ return "Dump node permission error";
+
+ }
return NULL;
}
@@ -2519,7 +2521,7 @@ static const char *dump_state_node_tree(FILE *fp, char *path)
if (fwrite(&sn, sizeof(sn), 1, fp) != 1)
return "Dump node state error";
- ret = dump_state_node_perms(fp, &sn, hdr->perms, hdr->num_perms);
+ ret = dump_state_node_perms(fp, hdr->perms, hdr->num_perms);
if (ret)
return ret;
diff --git a/tools/xenstore/xenstored_core.h b/tools/xenstore/xenstored_core.h
index 1cdbc3dcb5f7..b50ea3f57d5a 100644
--- a/tools/xenstore/xenstored_core.h
+++ b/tools/xenstore/xenstored_core.h
@@ -271,8 +271,7 @@ const char *dump_state_buffered_data(FILE *fp, const struct connection *c,
const struct connection *conn,
struct xs_state_connection *sc);
const char *dump_state_nodes(FILE *fp, const void *ctx);
-const char *dump_state_node_perms(FILE *fp, struct xs_state_node *sn,
- const struct xs_permissions *perms,
+const char *dump_state_node_perms(FILE *fp, const struct xs_permissions *perms,
unsigned int n_perms);
void read_state_global(const void *ctx, const void *state);
diff --git a/tools/xenstore/xenstored_domain.c b/tools/xenstore/xenstored_domain.c
index 3d4d0649a243..580ed454a3f5 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -1254,7 +1254,7 @@ static const char *dump_state_special_node(FILE *fp, const char *name,
if (fwrite(&sn, sizeof(sn), 1, fp) != 1)
return "Dump special node error";
- ret = dump_state_node_perms(fp, &sn, perms->p, perms->num);
+ ret = dump_state_node_perms(fp, perms->p, perms->num);
if (ret)
return ret;
--
2.17.1
next reply other threads:[~2021-05-06 16:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-06 16:12 Julien Grall [this message]
2021-05-07 15:45 ` [PATCH] tools/xenstored: Prevent a buffer overflow in dump_state_node_perms() Luca Fancellu
2021-05-10 7:49 ` Juergen Gross
2021-05-10 17:27 ` Julien Grall
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