| Message ID | 20180220130924.3698067-1-arnd@arndb.de |
|---|---|
| State | Accepted |
| Commit | 53b8d89ddbdbb0e4625a46d2cdbb6f106c52f801 |
| Headers | show |
| Series | md: raid5: avoid string overflow warning | expand |
On Tue, Feb 20, 2018 at 02:09:11PM +0100, Arnd Bergmann wrote: > gcc warns about a possible overflow of the kmem_cache string, when adding > four characters to a string of the same length: > > drivers/md/raid5.c: In function 'setup_conf': > drivers/md/raid5.c:2207:34: error: '-alt' directive writing 4 bytes into a region of size between 1 and 32 [-Werror=format-overflow=] > sprintf(conf->cache_name[1], "%s-alt", conf->cache_name[0]); > ^~~~ > drivers/md/raid5.c:2207:2: note: 'sprintf' output between 5 and 36 bytes into a destination of size 32 > sprintf(conf->cache_name[1], "%s-alt", conf->cache_name[0]); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > If I'm counting correctly, we need 11 characters for the fixed part > of the string and 18 characters for a 64-bit pointer (when no gendisk > is used), so that leaves three characters for conf->level, which should > always be sufficient. > > This makes the code use snprintf() with the correct length, to > make the code more robust against changes, and to get the compiler > to shut up. > > In commit f4be6b43f1ac ("md/raid5: ensure we create a unique name for > kmem_cache when mddev has no gendisk") from 2010, Neil said that > the pointer could be removed "shortly" once devices without gendisk > are disallowed. I have no idea if that happened, but if it did, that > should probably be changed as well. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Applied, thanks! > --- > drivers/md/raid5.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c > index 50d01144b805..7ef368061424 100644 > --- a/drivers/md/raid5.c > +++ b/drivers/md/raid5.c > @@ -2196,15 +2196,16 @@ static int grow_one_stripe(struct r5conf *conf, gfp_t gfp) > static int grow_stripes(struct r5conf *conf, int num) > { > struct kmem_cache *sc; > + size_t namelen = sizeof(conf->cache_name[0]); > int devs = max(conf->raid_disks, conf->previous_raid_disks); > > if (conf->mddev->gendisk) > - sprintf(conf->cache_name[0], > + snprintf(conf->cache_name[0], namelen, > "raid%d-%s", conf->level, mdname(conf->mddev)); > else > - sprintf(conf->cache_name[0], > + snprintf(conf->cache_name[0], namelen, > "raid%d-%p", conf->level, conf->mddev); > - sprintf(conf->cache_name[1], "%s-alt", conf->cache_name[0]); > + snprintf(conf->cache_name[1], namelen, "%.27s-alt", conf->cache_name[0]); > > conf->active_name = 0; > sc = kmem_cache_create(conf->cache_name[conf->active_name], > -- > 2.9.0 >
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 50d01144b805..7ef368061424 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -2196,15 +2196,16 @@ static int grow_one_stripe(struct r5conf *conf, gfp_t gfp) static int grow_stripes(struct r5conf *conf, int num) { struct kmem_cache *sc; + size_t namelen = sizeof(conf->cache_name[0]); int devs = max(conf->raid_disks, conf->previous_raid_disks); if (conf->mddev->gendisk) - sprintf(conf->cache_name[0], + snprintf(conf->cache_name[0], namelen, "raid%d-%s", conf->level, mdname(conf->mddev)); else - sprintf(conf->cache_name[0], + snprintf(conf->cache_name[0], namelen, "raid%d-%p", conf->level, conf->mddev); - sprintf(conf->cache_name[1], "%s-alt", conf->cache_name[0]); + snprintf(conf->cache_name[1], namelen, "%.27s-alt", conf->cache_name[0]); conf->active_name = 0; sc = kmem_cache_create(conf->cache_name[conf->active_name],
gcc warns about a possible overflow of the kmem_cache string, when adding four characters to a string of the same length: drivers/md/raid5.c: In function 'setup_conf': drivers/md/raid5.c:2207:34: error: '-alt' directive writing 4 bytes into a region of size between 1 and 32 [-Werror=format-overflow=] sprintf(conf->cache_name[1], "%s-alt", conf->cache_name[0]); ^~~~ drivers/md/raid5.c:2207:2: note: 'sprintf' output between 5 and 36 bytes into a destination of size 32 sprintf(conf->cache_name[1], "%s-alt", conf->cache_name[0]); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If I'm counting correctly, we need 11 characters for the fixed part of the string and 18 characters for a 64-bit pointer (when no gendisk is used), so that leaves three characters for conf->level, which should always be sufficient. This makes the code use snprintf() with the correct length, to make the code more robust against changes, and to get the compiler to shut up. In commit f4be6b43f1ac ("md/raid5: ensure we create a unique name for kmem_cache when mddev has no gendisk") from 2010, Neil said that the pointer could be removed "shortly" once devices without gendisk are disallowed. I have no idea if that happened, but if it did, that should probably be changed as well. Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/md/raid5.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) -- 2.9.0