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* [PATCH] tools/xenstored: Prevent a buffer overflow in dump_state_node_perms()
@ 2021-05-06 16:12 Julien Grall
  2021-05-07 15:45 ` Luca Fancellu
  2021-05-10  7:49 ` Juergen Gross
  0 siblings, 2 replies; 4+ messages in thread
From: Julien Grall @ 2021-05-06 16:12 UTC (permalink / raw)
  To: xen-devel; +Cc: julien, Julien Grall, Ian Jackson, Wei Liu, Juergen Gross

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



^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] tools/xenstored: Prevent a buffer overflow in dump_state_node_perms()
  2021-05-06 16:12 [PATCH] tools/xenstored: Prevent a buffer overflow in dump_state_node_perms() Julien Grall
@ 2021-05-07 15:45 ` Luca Fancellu
  2021-05-10  7:49 ` Juergen Gross
  1 sibling, 0 replies; 4+ messages in thread
From: Luca Fancellu @ 2021-05-07 15:45 UTC (permalink / raw)
  To: Julien Grall; +Cc: xen-devel, Julien Grall, Ian Jackson, Wei Liu, Juergen Gross



> On 6 May 2021, at 17:12, Julien Grall <julien@xen.org> wrote:
> 
> 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
> 
> 

Tested on FVP and another arm board, basic testing (run Xen, dom0, run one/two guests) - Everything fine.

Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>

Cheers,
Luca



^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] tools/xenstored: Prevent a buffer overflow in dump_state_node_perms()
  2021-05-06 16:12 [PATCH] tools/xenstored: Prevent a buffer overflow in dump_state_node_perms() Julien Grall
  2021-05-07 15:45 ` Luca Fancellu
@ 2021-05-10  7:49 ` Juergen Gross
  2021-05-10 17:27   ` Julien Grall
  1 sibling, 1 reply; 4+ messages in thread
From: Juergen Gross @ 2021-05-10  7:49 UTC (permalink / raw)
  To: Julien Grall, xen-devel; +Cc: Julien Grall, Ian Jackson, Wei Liu


[-- Attachment #1.1.1: Type: text/plain, Size: 1990 bytes --]

On 06.05.21 18:12, Julien Grall wrote:
> 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>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

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^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] tools/xenstored: Prevent a buffer overflow in dump_state_node_perms()
  2021-05-10  7:49 ` Juergen Gross
@ 2021-05-10 17:27   ` Julien Grall
  0 siblings, 0 replies; 4+ messages in thread
From: Julien Grall @ 2021-05-10 17:27 UTC (permalink / raw)
  To: Juergen Gross, xen-devel; +Cc: Julien Grall, Ian Jackson, Wei Liu

Hi Juergen,

On 10/05/2021 08:49, Juergen Gross wrote:
> On 06.05.21 18:12, Julien Grall wrote:
>> 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>
> 
> Reviewed-by: Juergen Gross <jgross@suse.com>

Committed.

Cheers,

-- 
Julien Grall


^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2021-05-10 17:27 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-05-06 16:12 [PATCH] tools/xenstored: Prevent a buffer overflow in dump_state_node_perms() Julien Grall
2021-05-07 15:45 ` Luca Fancellu
2021-05-10  7:49 ` Juergen Gross
2021-05-10 17:27   ` Julien Grall

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