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Subject[PATCH 1/2] staging: unisys: visorbus: address theoretical int overflows
Date
From: Tim Sell <Timothy.Sell@unisys.com>

Add necessary casting to several places where we were doing 32-bit
arithmetic (unsigned) to produce a 64-bit (unsigned long) result, to
prevent the theoretical possibility of a 32-bit overflow during the
arithmetic.

FYI, these are unsigned long:

ctx->param_bytes
ctx->allocbytes

These are unsigned int:

bytes
phdr->name_offset
phdr->name_length

Here is the test program demonstrating why we really need the casts:

void main()
{
unsigned int i;
unsigned long il;

printf("sizeof(int) =%dn",sizeof(i));
printf("sizeof(long)=%dn",sizeof(il));

i = (unsigned int)((((unsigned long)(1)) << 32) - 1);
printf("i = %un", i);
il = i+1;
printf("adding 1 withOUT cast = %lun", il);
il = (unsigned long)i+1;
printf("adding 1 WITH cast = %lun", il);
}
[selltc@mac tmp]$ gcc x.c -o x.out
[selltc@mac tmp]$ ./x.out
sizeof(int) =4
sizeof(long)=8
i = 4294967295
adding 1 withOUT cast = 0
adding 1 WITH cast = 4294967296

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Reviewed-by: David Binder <david.binder@unisys.com>
---
drivers/staging/unisys/visorbus/visorchipset.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/unisys/visorbus/visorchipset.c b/drivers/staging/unisys/visorbus/visorchipset.c
index fed554a4..ef2823a 100644
--- a/drivers/staging/unisys/visorbus/visorchipset.c
+++ b/drivers/staging/unisys/visorbus/visorchipset.c
@@ -590,7 +590,8 @@ static void *parser_name_get(struct parser_context *ctx)
struct visor_controlvm_parameters_header *phdr;

phdr = &ctx->data;
- if (phdr->name_offset + phdr->name_length > ctx->param_bytes)
+ if ((unsigned long)phdr->name_offset +
+ (unsigned long)phdr->name_length > ctx->param_bytes)
return NULL;
ctx->curr = (char *)&phdr + phdr->name_offset;
ctx->bytes_remaining = phdr->name_length;
@@ -1317,13 +1318,13 @@ static void parser_done(struct parser_context *ctx)
static struct parser_context *parser_init_stream(u64 addr, u32 bytes,
bool *retry)
{
- int allocbytes;
+ unsigned long allocbytes;
struct parser_context *ctx;
void *mapping;

*retry = false;
/* alloc an extra byte to ensure payload is \0 terminated */
- allocbytes = bytes + 1 + (sizeof(struct parser_context) -
+ allocbytes = (unsigned long)bytes + 1 + (sizeof(struct parser_context) -
sizeof(struct visor_controlvm_parameters_header));
if ((chipset_dev->controlvm_payload_bytes_buffered + bytes) >
MAX_CONTROLVM_PAYLOAD_BYTES) {
--
1.9.1
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