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staging: unisys: visorbus: address theoretical int overflows 

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tim Sell 2017-11-17 12:27:38 -05:00 committed by Greg Kroah-Hartman
parent 1c0c275b11
commit a5eb2188f5
1 changed files with 4 additions and 3 deletions
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7
drivers/staging/unisys/visorbus/visorchipset.c
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@ -581,7 +581,8 @@ 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;
@ -1308,13 +1309,13 @@ 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) {