| Message ID | 20210323124624.1494552-1-arnd@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: zoned: fix uninitialized max_chunk_size | expand |
On Tue, Mar 23, 2021 at 01:46:19PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > The ctl->max_chunk_size member might be used uninitialized > when none of the three conditions for initializing it in > init_alloc_chunk_ctl_policy_zoned() are true: > > In function ‘init_alloc_chunk_ctl_policy_zoned’, > inlined from ‘init_alloc_chunk_ctl’ at fs/btrfs/volumes.c:5023:3, > inlined from ‘btrfs_alloc_chunk’ at fs/btrfs/volumes.c:5340:2: > include/linux/compiler-gcc.h:48:45: error: ‘ctl.max_chunk_size’ may be used uninitialized [-Werror=maybe-uninitialized] > 4998 | ctl->max_chunk_size = min(limit, ctl->max_chunk_size); > | ^~~ > fs/btrfs/volumes.c: In function ‘btrfs_alloc_chunk’: > fs/btrfs/volumes.c:5316:32: note: ‘ctl’ declared here > 5316 | struct alloc_chunk_ctl ctl; > | ^~~ > > Initialize it to UINT_MAX and rely on the min() expression to limit > it. > > Fixes: 1cd6121f2a38 ("btrfs: zoned: implement zoned chunk allocator") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > Note that the -Wmaybe-unintialized warning is globally disabled > by default. For some reason I got this warning anyway when building > this specific file with gcc-11. The warning catches a theoretical case but this would not happen in pracitce. There are three bits to check and that covers all valid options, but there should be a final else {} like is in init_alloc_chunk_ctl_policy_regular that does not let the function continue as that would mean there are worse problems. btrfs_alloc_chunk init_alloc_chunk_ctl init_alloc_chunk_ctl_policy_zoned and btrfs_alloc_chunk validates the ctl->flags against BTRFS_BLOCK_GROUP_TYPE_MASK, which is exactly the tree branches. > --- > fs/btrfs/volumes.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index bc3b33efddc5..b42b423b6a10 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -4980,6 +4980,7 @@ static void init_alloc_chunk_ctl_policy_zoned( > u64 type = ctl->type; > > ctl->max_stripe_size = zone_size; > + ctl->max_chunk_size = UINT_MAX; This would allow the min() work but otherwise is not an expected to happen at all. > if (type & BTRFS_BLOCK_GROUP_DATA) { > ctl->max_chunk_size = round_down(BTRFS_MAX_DATA_CHUNK_SIZE, > zone_size); > -- > 2.29.2
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index bc3b33efddc5..b42b423b6a10 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -4980,6 +4980,7 @@ static void init_alloc_chunk_ctl_policy_zoned( u64 type = ctl->type; ctl->max_stripe_size = zone_size; + ctl->max_chunk_size = UINT_MAX; if (type & BTRFS_BLOCK_GROUP_DATA) { ctl->max_chunk_size = round_down(BTRFS_MAX_DATA_CHUNK_SIZE, zone_size);