From: Dan Streetman <ddstreet@xxxxxxxx> Subject: zswap: disable changing params if init fails Add zswap_init_failed bool that prevents changing any of the module params, if init_zswap() fails, and set zswap_enabled to false. Change 'enabled' param to a callback, and check zswap_init_failed before allowing any change to 'enabled', 'zpool', or 'compressor' params. Any driver that is built-in to the kernel will not be unloaded if its init function returns error, and its module params remain accessible for users to change via sysfs. Since zswap uses param callbacks, which assume that zswap has been initialized, changing the zswap params after a failed initialization will result in WARNING due to the param callbacks expecting a pool to already exist. This prevents that by immediately exiting any of the param callbacks if initialization failed. This was reported here: https://marc.info/?l=linux-mm&m=147004228125528&w=4 And fixes this WARNING: [ 429.723476] WARNING: CPU: 0 PID: 5140 at mm/zswap.c:503 __zswap_pool_current+0x56/0x60 The warning is just noise, and not serious. However, when init fails, zswap frees all its percpu dstmem pages and its kmem cache. The kmem cache might be serious, if kmem_cache_alloc(NULL, gfp) has problems; but the percpu dstmem pages are definitely a problem, as they're used as temporary buffer for compressed pages before copying into place in the zpool. If the user does get zswap enabled after an init failure, then zswap will likely Oops on the first page it tries to compress (or worse, start corrupting memory). Fixes: 90b0fc26d5db ("zswap: change zpool/compressor at runtime") Link: http://lkml.kernel.org/r/20170124200259.16191-2-ddstreet@xxxxxxxx Signed-off-by: Dan Streetman <dan.streetman@xxxxxxxxxxxxx> Reported-by: Marcin Miroslaw <marcin@xxxxxxxx> Cc: Seth Jennings <sjenning@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/zswap.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff -puN mm/zswap.c~zswap-disable-changing-params-if-init-fails mm/zswap.c --- a/mm/zswap.c~zswap-disable-changing-params-if-init-fails +++ a/mm/zswap.c @@ -78,7 +78,13 @@ static u64 zswap_duplicate_entry; /* Enable/disable zswap (disabled by default) */ static bool zswap_enabled; -module_param_named(enabled, zswap_enabled, bool, 0644); +static int zswap_enabled_param_set(const char *, + const struct kernel_param *); +static struct kernel_param_ops zswap_enabled_param_ops = { + .set = zswap_enabled_param_set, + .get = param_get_bool, +}; +module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644); /* Crypto compressor to use */ #define ZSWAP_COMPRESSOR_DEFAULT "lzo" @@ -176,6 +182,9 @@ static atomic_t zswap_pools_count = ATOM /* used by param callback function */ static bool zswap_init_started; +/* fatal error during init */ +static bool zswap_init_failed; + /********************************* * helpers and fwd declarations **********************************/ @@ -624,6 +633,11 @@ static int __zswap_param_set(const char char *s = strstrip((char *)val); int ret; + if (zswap_init_failed) { + pr_err("can't set param, initialization failed\n"); + return -ENODEV; + } + /* no change required */ if (!strcmp(s, *(char **)kp->arg)) return 0; @@ -703,6 +717,17 @@ static int zswap_zpool_param_set(const c return __zswap_param_set(val, kp, NULL, zswap_compressor); } +static int zswap_enabled_param_set(const char *val, + const struct kernel_param *kp) +{ + if (zswap_init_failed) { + pr_err("can't enable, initialization failed\n"); + return -ENODEV; + } + + return param_set_bool(val, kp); +} + /********************************* * writeback code **********************************/ @@ -1201,6 +1226,9 @@ hp_fail: dstmem_fail: zswap_entry_cache_destroy(); cache_fail: + /* if built-in, we aren't unloaded on failure; don't allow use */ + zswap_init_failed = true; + zswap_enabled = false; return -ENOMEM; } /* must be late so crypto has time to come up */ _ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html