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[PATCH] scsi/qemu-pr-helper: Fix out-of-bounds access to trnptid_list[]
From: |
Christophe de Dinechin |
Subject: |
[PATCH] scsi/qemu-pr-helper: Fix out-of-bounds access to trnptid_list[] |
Date: |
Fri, 28 Feb 2020 16:00:59 +0100 |
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 <address@hidden>
---
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
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