lkml.org 
[lkml]   [2017]   [Aug]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [PATCH] crypto: ccp - avoid uninitialized variable warning
From
Date
On 07/31/2017 03:49 PM, Arnd Bergmann wrote:
> The added support for version 5 CCPs introduced a false-positive
> warning in the RSA implementation:
>
> drivers/crypto/ccp/ccp-ops.c: In function 'ccp_run_rsa_cmd':
> drivers/crypto/ccp/ccp-ops.c:1856:3: error: 'sb_count' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>
> This changes the code in a way that should make it easier for
> the compiler to track the state of the sb_count variable, and
> avoid the warning.
>
> Fixes: 6ba46c7d4d7e ("crypto: ccp - Fix base RSA function for version 5 CCPs")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/crypto/ccp/ccp-ops.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/crypto/ccp/ccp-ops.c b/drivers/crypto/ccp/ccp-ops.c
> index 40c062ad8726..a8bc207b099a 100644
> --- a/drivers/crypto/ccp/ccp-ops.c
> +++ b/drivers/crypto/ccp/ccp-ops.c
> @@ -1758,6 +1758,7 @@ static int ccp_run_rsa_cmd(struct ccp_cmd_queue *cmd_q, struct ccp_cmd *cmd)
> o_len = 32 * ((rsa->key_size + 255) / 256);
> i_len = o_len * 2;
>
> + sb_count = 0;
> if (cmd_q->ccp->vdata->version < CCP_VERSION(5, 0)) {
> /* sb_count is the number of storage block slots required
> * for the modulus.
> @@ -1852,7 +1853,7 @@ static int ccp_run_rsa_cmd(struct ccp_cmd_queue *cmd_q, struct ccp_cmd *cmd)
> ccp_dm_free(&exp);
>
> e_sb:
> - if (cmd_q->ccp->vdata->version < CCP_VERSION(5, 0))
> + if (sb_count)
> cmd_q->ccp->vdata->perform->sbfree(cmd_q, op.sb_key, sb_count);
>
> return ret;
>

This is a fine solution. However, having lived with this annoyance for a
while, and even hoping that a
a later compiler fixes it, I would have preferred to either:

1) Initialize the local variable at declaration time, or

2) Use this patch, which the compiler could optimize as it sees fit, and
maintains a clear distinction
for the code path for older devices:

diff --git a/drivers/crypto/ccp/ccp-ops.c b/drivers/crypto/ccp/ccp-ops.c
index 40c062a..a3a884a 100644
--- a/drivers/crypto/ccp/ccp-ops.c
+++ b/drivers/crypto/ccp/ccp-ops.c
@@ -1733,7 +1733,7 @@ static int ccp_run_rsa_cmd(struct ccp_cmd_queue
*cmd_q, struct ccp_cmd *cmd)
struct ccp_rsa_engine *rsa = &cmd->u.rsa;
struct ccp_dm_workarea exp, src, dst;
struct ccp_op op;
- unsigned int sb_count, i_len, o_len;
+ unsigned int i_len, o_len;
int ret;

/* Check against the maximum allowable size, in bits */
@@ -1762,7 +1762,7 @@ static int ccp_run_rsa_cmd(struct ccp_cmd_queue
*cmd_q, struct ccp_cmd *cmd)
/* sb_count is the number of storage block slots required
* for the modulus.
*/
- sb_count = o_len / CCP_SB_BYTES;
+ unsigned int sb_count = o_len / CCP_SB_BYTES;
op.sb_key = cmd_q->ccp->vdata->perform->sballoc(cmd_q,
sb_count);
if (!op.sb_key)
@@ -1853,7 +1853,10 @@ static int ccp_run_rsa_cmd(struct ccp_cmd_queue
*cmd_q, struct ccp_cmd *cmd)

e_sb:
if (cmd_q->ccp->vdata->version < CCP_VERSION(5, 0))
+ {
+ unsigned int sb_count = o_len / CCP_SB_BYTES;
cmd_q->ccp->vdata->perform->sbfree(cmd_q, op.sb_key,
sb_count);
+ }

return ret;
}

Discuss?

\
 
 \ /
  Last update: 2017-08-01 16:53    [W:0.064 / U:0.604 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site