Le 14/04/2020 à 20:34, Jason Gunthorpe a écrit :
On Sat, Mar 28, 2020 at 08:30:40AM +0100, Christophe JAILLET wrote:
There is an off-by-one issue when checking if there is enough space in the
output buffer, because we must keep some place for a final '\0'.
While at it:
- Use 'scnprintf' instead of 'snprintf' in order to avoid a superfluous
'strlen'
- avoid some useless initializations
- avoida hard coded buffer size that can be computed at built time.
Fixes: a51f06e1679e ("RDMA/ocrdma: Query controller information")
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
The '\0' comes from memset(..., 0, ...) in all callers.
This could be also avoided if needed.
---
drivers/infiniband/hw/ocrdma/ocrdma_stats.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/infiniband/hw/ocrdma/ocrdma_stats.c b/drivers/infiniband/hw/ocrdma/ocrdma_stats.c
index 5f831e3bdbad..614a449e6b87 100644
--- a/drivers/infiniband/hw/ocrdma/ocrdma_stats.c
+++ b/drivers/infiniband/hw/ocrdma/ocrdma_stats.c
@@ -49,13 +49,12 @@ static struct dentry *ocrdma_dbgfs_dir;
static int ocrdma_add_stat(char *start, char *pcur,
char *name, u64 count)
{
- char buff[128] = {0};
- int cpy_len = 0;
+ char buff[128];
+ int cpy_len;
- snprintf(buff, 128, "%s: %llu\n", name, count);
- cpy_len = strlen(buff);
+ cpy_len = scnprintf(buff, sizeof(buff), "%s: %llu\n", name, count);
- if (pcur + cpy_len > start + OCRDMA_MAX_DBGFS_MEM) {
+ if (pcur + cpy_len >= start + OCRDMA_MAX_DBGFS_MEM) {
pr_err("%s: No space in stats buff\n", __func__);
return 0;
}
The memcpy is still kind of silly right? What about this:
static int ocrdma_add_stat(char *start, char *pcur, char *name, u64 count)
{
size_t len = (start + OCRDMA_MAX_DBGFS_MEM) - pcur;
int cpy_len;
cpy_len = snprintf(pcur, len, "%s: %llu\n", name, count);
if (cpy_len >= len || cpy_len < 0) {
pr_err("%s: No space in stats buff\n", __func__);
return 0;
}
return cpy_len;
}
Jason
It can looks useless, but I think that the goal was to make sure that we
would not display truncated data. Each line is either complete or absent.
I don't have any strong opinion of what is best, but I can understand
the current logic.
This function is not a hot spot, so useless memcpy is not a big issue.
CJ
