Messages in this thread | | | Date | Tue, 14 Apr 2020 15:34:41 -0300 | From | Jason Gunthorpe <> | Subject | Re: [PATCH] RDMA/ocrdma: Fix an off-by-one issue in 'ocrdma_add_stat' |
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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@wanadoo.fr> > --- > 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
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