* [PATCH] scsi/qemu-pr-helper: Fix out-of-bounds access to trnptid_list[]
@ 2020-02-28 15:00 Christophe de Dinechin
2020-03-02 15:38 ` Paolo Bonzini
2020-03-16 21:06 ` Paolo Bonzini
0 siblings, 2 replies; 3+ messages in thread
From: Christophe de Dinechin @ 2020-02-28 15:00 UTC (permalink / raw)
To: qemu-devel; +Cc: Fam Zheng, Paolo Bonzini, qemu-block
Compile error reported by gcc 10.0.1:
scsi/qemu-pr-helper.c: In function ‘multipath_pr_out’:
scsi/qemu-pr-helper.c:523:32: error: array subscript <unknown> is outside array bounds of ‘struct transportid *[0]’ [-Werror=array-bounds]
523 | paramp.trnptid_list[paramp.num_transportid++] = id;
| ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from scsi/qemu-pr-helper.c:36:
/usr/include/mpath_persist.h:168:22: note: while referencing ‘trnptid_list’
168 | struct transportid *trnptid_list[];
| ^~~~~~~~~~~~
scsi/qemu-pr-helper.c:424:35: note: defined here ‘paramp’
424 | struct prout_param_descriptor paramp;
| ^~~~~~
This highlights an actual implementation issue in function multipath_pr_out.
The variable paramp is declared with type `struct prout_param_descriptor`,
which is a struct terminated by an empty array in mpath_persist.h:
struct transportid *trnptid_list[];
That empty array was filled with code that looked like that:
trnptid_list[paramp.descr.num_transportid++] = id;
This is an actual out-of-bounds access.
The fix is to replace `paramp` with an anonymous struct that adds
additional space for the data, called `trnptid_list_storage`.
That space provides MATH_MX_TIDS entries, and is not accessed directly
but through a pointer to `descr.trnptid_list`, in the unlikely case a
future compiler inserts some padding between the two structs.
Signed-off-by: Christophe de Dinechin <dinechin@redhat.com>
---
scsi/qemu-pr-helper.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/scsi/qemu-pr-helper.c b/scsi/qemu-pr-helper.c
index 0659ceef09..01013221b3 100644
--- a/scsi/qemu-pr-helper.c
+++ b/scsi/qemu-pr-helper.c
@@ -421,7 +421,12 @@ static int multipath_pr_out(int fd, const uint8_t *cdb, uint8_t *sense,
int rq_servact = cdb[1];
int rq_scope = cdb[2] >> 4;
int rq_type = cdb[2] & 0xf;
- struct prout_param_descriptor paramp;
+ struct
+ {
+ struct prout_param_descriptor descr;
+ struct transportid *trnptid_list_storage[MPATH_MX_TIDS];
+ } paramp;
+ struct transportid **trnptid_list = paramp.descr.trnptid_list;
char transportids[PR_HELPER_DATA_SIZE];
int r;
@@ -455,9 +460,9 @@ static int multipath_pr_out(int fd, const uint8_t *cdb, uint8_t *sense,
* do the opposite).
*/
memset(¶mp, 0, sizeof(paramp));
- memcpy(¶mp.key, ¶m[0], 8);
- memcpy(¶mp.sa_key, ¶m[8], 8);
- paramp.sa_flags = param[20];
+ memcpy(¶mp.descr.key, ¶m[0], 8);
+ memcpy(¶mp.descr.sa_key, ¶m[8], 8);
+ paramp.descr.sa_flags = param[20];
if (sz > PR_OUT_FIXED_PARAM_SIZE) {
size_t transportid_len;
int i, j;
@@ -520,12 +525,13 @@ static int multipath_pr_out(int fd, const uint8_t *cdb, uint8_t *sense,
return CHECK_CONDITION;
}
- paramp.trnptid_list[paramp.num_transportid++] = id;
+ assert(paramp.descr.num_transportid < MPATH_MX_TIDS);
+ trnptid_list[paramp.descr.num_transportid++] = id;
}
}
r = mpath_persistent_reserve_out(fd, rq_servact, rq_scope, rq_type,
- ¶mp, noisy, verbose);
+ ¶mp.descr, noisy, verbose);
return mpath_reconstruct_sense(fd, r, sense);
}
#endif
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] scsi/qemu-pr-helper: Fix out-of-bounds access to trnptid_list[]
2020-02-28 15:00 [PATCH] scsi/qemu-pr-helper: Fix out-of-bounds access to trnptid_list[] Christophe de Dinechin
@ 2020-03-02 15:38 ` Paolo Bonzini
2020-03-16 21:06 ` Paolo Bonzini
1 sibling, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2020-03-02 15:38 UTC (permalink / raw)
To: Christophe de Dinechin, qemu-devel; +Cc: Fam Zheng, qemu-stable, qemu-block
On 28/02/20 16:00, Christophe de Dinechin wrote:
> Compile error reported by gcc 10.0.1:
>
> scsi/qemu-pr-helper.c: In function ‘multipath_pr_out’:
> scsi/qemu-pr-helper.c:523:32: error: array subscript <unknown> is outside array bounds of ‘struct transportid *[0]’ [-Werror=array-bounds]
> 523 | paramp.trnptid_list[paramp.num_transportid++] = id;
> | ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from scsi/qemu-pr-helper.c:36:
> /usr/include/mpath_persist.h:168:22: note: while referencing ‘trnptid_list’
> 168 | struct transportid *trnptid_list[];
> | ^~~~~~~~~~~~
> scsi/qemu-pr-helper.c:424:35: note: defined here ‘paramp’
> 424 | struct prout_param_descriptor paramp;
> | ^~~~~~
Ouch. Very nice new warning.
Cc: qemu-stable@nongnu.org
Queued, thanks.
> This highlights an actual implementation issue in function multipath_pr_out.
> The variable paramp is declared with type `struct prout_param_descriptor`,
> which is a struct terminated by an empty array in mpath_persist.h:
>
> struct transportid *trnptid_list[];
>
> That empty array was filled with code that looked like that:
>
> trnptid_list[paramp.descr.num_transportid++] = id;
>
> This is an actual out-of-bounds access.
>
> The fix is to replace `paramp` with an anonymous struct that adds
> additional space for the data, called `trnptid_list_storage`.
> That space provides MATH_MX_TIDS entries, and is not accessed directly
> but through a pointer to `descr.trnptid_list`, in the unlikely case a
> future compiler inserts some padding between the two structs.
>
> Signed-off-by: Christophe de Dinechin <dinechin@redhat.com>
> ---
> scsi/qemu-pr-helper.c | 18 ++++++++++++------
> 1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/scsi/qemu-pr-helper.c b/scsi/qemu-pr-helper.c
> index 0659ceef09..01013221b3 100644
> --- a/scsi/qemu-pr-helper.c
> +++ b/scsi/qemu-pr-helper.c
> @@ -421,7 +421,12 @@ static int multipath_pr_out(int fd, const uint8_t *cdb, uint8_t *sense,
> int rq_servact = cdb[1];
> int rq_scope = cdb[2] >> 4;
> int rq_type = cdb[2] & 0xf;
> - struct prout_param_descriptor paramp;
> + struct
> + {
> + struct prout_param_descriptor descr;
> + struct transportid *trnptid_list_storage[MPATH_MX_TIDS];
> + } paramp;
> + struct transportid **trnptid_list = paramp.descr.trnptid_list;
> char transportids[PR_HELPER_DATA_SIZE];
> int r;
>
> @@ -455,9 +460,9 @@ static int multipath_pr_out(int fd, const uint8_t *cdb, uint8_t *sense,
> * do the opposite).
> */
> memset(¶mp, 0, sizeof(paramp));
> - memcpy(¶mp.key, ¶m[0], 8);
> - memcpy(¶mp.sa_key, ¶m[8], 8);
> - paramp.sa_flags = param[20];
> + memcpy(¶mp.descr.key, ¶m[0], 8);
> + memcpy(¶mp.descr.sa_key, ¶m[8], 8);
> + paramp.descr.sa_flags = param[20];
> if (sz > PR_OUT_FIXED_PARAM_SIZE) {
> size_t transportid_len;
> int i, j;
> @@ -520,12 +525,13 @@ static int multipath_pr_out(int fd, const uint8_t *cdb, uint8_t *sense,
> return CHECK_CONDITION;
> }
>
> - paramp.trnptid_list[paramp.num_transportid++] = id;
> + assert(paramp.descr.num_transportid < MPATH_MX_TIDS);
> + trnptid_list[paramp.descr.num_transportid++] = id;
> }
> }
>
> r = mpath_persistent_reserve_out(fd, rq_servact, rq_scope, rq_type,
> - ¶mp, noisy, verbose);
> + ¶mp.descr, noisy, verbose);
> return mpath_reconstruct_sense(fd, r, sense);
> }
> #endif
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] scsi/qemu-pr-helper: Fix out-of-bounds access to trnptid_list[]
2020-02-28 15:00 [PATCH] scsi/qemu-pr-helper: Fix out-of-bounds access to trnptid_list[] Christophe de Dinechin
2020-03-02 15:38 ` Paolo Bonzini
@ 2020-03-16 21:06 ` Paolo Bonzini
1 sibling, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2020-03-16 21:06 UTC (permalink / raw)
To: Christophe de Dinechin, qemu-devel; +Cc: Fam Zheng, qemu-block
On 28/02/20 16:00, Christophe de Dinechin wrote:
> Compile error reported by gcc 10.0.1:
>
> scsi/qemu-pr-helper.c: In function ‘multipath_pr_out’:
> scsi/qemu-pr-helper.c:523:32: error: array subscript <unknown> is outside array bounds of ‘struct transportid *[0]’ [-Werror=array-bounds]
> 523 | paramp.trnptid_list[paramp.num_transportid++] = id;
> | ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from scsi/qemu-pr-helper.c:36:
> /usr/include/mpath_persist.h:168:22: note: while referencing ‘trnptid_list’
> 168 | struct transportid *trnptid_list[];
> | ^~~~~~~~~~~~
> scsi/qemu-pr-helper.c:424:35: note: defined here ‘paramp’
> 424 | struct prout_param_descriptor paramp;
> | ^~~~~~
>
> This highlights an actual implementation issue in function multipath_pr_out.
> The variable paramp is declared with type `struct prout_param_descriptor`,
> which is a struct terminated by an empty array in mpath_persist.h:
>
> struct transportid *trnptid_list[];
>
> That empty array was filled with code that looked like that:
>
> trnptid_list[paramp.descr.num_transportid++] = id;
>
> This is an actual out-of-bounds access.
The fix unfortunately causes a compilation warning-turned-error because
of a flexible array member in the middle of a struct. The simplest fix
is just to malloc the struct:
diff --git a/scsi/qemu-pr-helper.c b/scsi/qemu-pr-helper.c
index 0101322..65a8261 100644
--- a/scsi/qemu-pr-helper.c
+++ b/scsi/qemu-pr-helper.c
@@ -421,15 +421,13 @@ static int multipath_pr_out(int fd, const uint8_t *cdb, uint8_t *sense,
int rq_servact = cdb[1];
int rq_scope = cdb[2] >> 4;
int rq_type = cdb[2] & 0xf;
- struct
- {
- struct prout_param_descriptor descr;
- struct transportid *trnptid_list_storage[MPATH_MX_TIDS];
- } paramp;
- struct transportid **trnptid_list = paramp.descr.trnptid_list;
+ g_autofree struct prout_param_descriptor *paramp = NULL;
char transportids[PR_HELPER_DATA_SIZE];
int r;
+ paramp = g_malloc0(sizeof(struct prout_param_descriptor)
+ + sizeof(struct transportid *) * MPATH_MX_TIDS);
+
if (sz < PR_OUT_FIXED_PARAM_SIZE) {
/* Illegal request, Parameter list length error. This isn't fatal;
* we have read the data, send an error without closing the socket.
@@ -459,10 +457,9 @@ static int multipath_pr_out(int fd, const uint8_t *cdb, uint8_t *sense,
* used by libmpathpersist (which, of course, will immediately
* do the opposite).
*/
- memset(¶mp, 0, sizeof(paramp));
- memcpy(¶mp.descr.key, ¶m[0], 8);
- memcpy(¶mp.descr.sa_key, ¶m[8], 8);
- paramp.descr.sa_flags = param[20];
+ memcpy(¶mp->key, ¶m[0], 8);
+ memcpy(¶mp->sa_key, ¶m[8], 8);
+ paramp->sa_flags = param[20];
if (sz > PR_OUT_FIXED_PARAM_SIZE) {
size_t transportid_len;
int i, j;
@@ -525,13 +522,13 @@ static int multipath_pr_out(int fd, const uint8_t *cdb, uint8_t *sense,
return CHECK_CONDITION;
}
- assert(paramp.descr.num_transportid < MPATH_MX_TIDS);
- trnptid_list[paramp.descr.num_transportid++] = id;
+ assert(paramp->num_transportid < MPATH_MX_TIDS);
+ paramp->trnptid_list[paramp->num_transportid++] = id;
}
}
r = mpath_persistent_reserve_out(fd, rq_servact, rq_scope, rq_type,
- ¶mp.descr, noisy, verbose);
+ paramp, noisy, verbose);
return mpath_reconstruct_sense(fd, r, sense);
}
#endif
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2020-02-28 15:00 [PATCH] scsi/qemu-pr-helper: Fix out-of-bounds access to trnptid_list[] Christophe de Dinechin
2020-03-02 15:38 ` Paolo Bonzini
2020-03-16 21:06 ` Paolo Bonzini
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