| Message ID | 1469670123-19839-1-git-send-email-bo.li.liu@oracle.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Wed, 27 Jul 2016 18:42:03 -0700, Liu Bo wrote: > Function start_transaction() can return ERR_PTR(1) when flush is > BTRFS_RESERVE_FLUSH_LIMIT, so the call graph is > > start_transaction (return ERR_PTR(1)) > -> btrfs_block_rsv_add (return 1) > -> reserve_metadata_bytes (return 1) > -> flush_space (return 1) > -> do_chunk_alloc (return 1) > > With BTRFS_RESERVE_FLUSH_LIMIT, if flush_space is already on the > flush_state of ALLOC_CHUNK and it successfully allocates a new > chunk, then instead of trying to reserve space again, > reserve_metadata_bytes returns 1 immediately. > > Eventually the callers who call start_transaction() usually just > do the IS_ERR() check which ERR_PTR(1) can pass, then it'll get > a panic when dereferencing a pointer which is ERR_PTR(1). > > This makes flush_space() translate 'ret = 1' to 'ret = 0'. > > Signed-off-by: Liu Bo <bo.li.liu@oracle.com> > --- > We found this 'NULL pointer dereference' on an old 3.8 kernel but > it's not going to happen on the upstream since there is no caller > of btrfs_start_transaction_lflush(). > > fs/btrfs/extent-tree.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index 7a35c9d..a00fb67 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -4457,6 +4457,15 @@ void check_system_chunk(struct btrfs_trans_handle *trans, > } > } > > +/* > + * If force is CHUNK_ALLOC_FORCE: > + * - return 1 if it successfully allocates a chunk, > + * - return errors including -ENOSPC otherwise. > + * If force is NOT CHUNK_ALLOC_FORCE: > + * - return 0 if it doesn't need to allocate a new chunk, > + * - return 1 if it successfully allocates a chunk, > + * - return errors including -ENOSPC otherwise. > + */ > static int do_chunk_alloc(struct btrfs_trans_handle *trans, > struct btrfs_root *extent_root, u64 flags, int force) > { > @@ -4857,7 +4866,7 @@ static int flush_space(struct btrfs_root *root, > btrfs_get_alloc_profile(root, 0), > CHUNK_ALLOC_NO_FORCE); > btrfs_end_transaction(trans, root); > - if (ret == -ENOSPC) > + if (ret == -ENOSPC || ret == 1) > ret = 0; > break; > case COMMIT_TRANS: > -- > 2.5.5 For reviewers - this came up before here: https://patchwork.kernel.org/patch/7778651/ Same fix basically. -h -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Jul 28, 2016 at 03:36:53PM +0000, Holger Hoffstätte wrote: > On Wed, 27 Jul 2016 18:42:03 -0700, Liu Bo wrote: > > > Function start_transaction() can return ERR_PTR(1) when flush is > > BTRFS_RESERVE_FLUSH_LIMIT, so the call graph is > > > > start_transaction (return ERR_PTR(1)) > > -> btrfs_block_rsv_add (return 1) > > -> reserve_metadata_bytes (return 1) > > -> flush_space (return 1) > > -> do_chunk_alloc (return 1) > > > > With BTRFS_RESERVE_FLUSH_LIMIT, if flush_space is already on the > > flush_state of ALLOC_CHUNK and it successfully allocates a new > > chunk, then instead of trying to reserve space again, > > reserve_metadata_bytes returns 1 immediately. > > > > Eventually the callers who call start_transaction() usually just > > do the IS_ERR() check which ERR_PTR(1) can pass, then it'll get > > a panic when dereferencing a pointer which is ERR_PTR(1). > > > > This makes flush_space() translate 'ret = 1' to 'ret = 0'. > > > > Signed-off-by: Liu Bo <bo.li.liu@oracle.com> > > --- > > We found this 'NULL pointer dereference' on an old 3.8 kernel but > > it's not going to happen on the upstream since there is no caller > > of btrfs_start_transaction_lflush(). > > > > fs/btrfs/extent-tree.c | 11 ++++++++++- > > 1 file changed, 10 insertions(+), 1 deletion(-) > > > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > > index 7a35c9d..a00fb67 100644 > > --- a/fs/btrfs/extent-tree.c > > +++ b/fs/btrfs/extent-tree.c > > @@ -4457,6 +4457,15 @@ void check_system_chunk(struct btrfs_trans_handle *trans, > > } > > } > > > > +/* > > + * If force is CHUNK_ALLOC_FORCE: > > + * - return 1 if it successfully allocates a chunk, > > + * - return errors including -ENOSPC otherwise. > > + * If force is NOT CHUNK_ALLOC_FORCE: > > + * - return 0 if it doesn't need to allocate a new chunk, > > + * - return 1 if it successfully allocates a chunk, > > + * - return errors including -ENOSPC otherwise. > > + */ > > static int do_chunk_alloc(struct btrfs_trans_handle *trans, > > struct btrfs_root *extent_root, u64 flags, int force) > > { > > @@ -4857,7 +4866,7 @@ static int flush_space(struct btrfs_root *root, > > btrfs_get_alloc_profile(root, 0), > > CHUNK_ALLOC_NO_FORCE); > > btrfs_end_transaction(trans, root); > > - if (ret == -ENOSPC) > > + if (ret == -ENOSPC || ret == 1) > > ret = 0; > > break; > > case COMMIT_TRANS: > > -- > > 2.5.5 > > For reviewers - this came up before here: > https://patchwork.kernel.org/patch/7778651/ > > Same fix basically. Aha, I've given it my Reviewed-by. Taking either one works for me, I can make the clarifying comment into a seperate patch if we need to. Thanks, -liubo -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Jul 28, 2016 at 11:49:14AM -0700, Liu Bo wrote: > > For reviewers - this came up before here: > > https://patchwork.kernel.org/patch/7778651/ > > > > Same fix basically. > > Aha, I've given it my Reviewed-by. > > Taking either one works for me, I can make the clarifying comment into a > seperate patch if we need to. I'll pick the first patch and please send the separate comment update. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Jul 29, 2016 at 07:01:50PM +0200, David Sterba wrote: > On Thu, Jul 28, 2016 at 11:49:14AM -0700, Liu Bo wrote: > > > For reviewers - this came up before here: > > > https://patchwork.kernel.org/patch/7778651/ David, this patch made a mistake in commit log. > > > > > > Same fix basically. > > > > Aha, I've given it my Reviewed-by. > > > > Taking either one works for me, I can make the clarifying comment into a > > seperate patch if we need to. > > I'll pick the first patch and please send the separate comment update. > Thanks. Sure. Thanks, -liubo -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
David, Holger, Thank you for picking up that old patch of mine. Alex. On Fri, Jul 29, 2016 at 8:53 PM, Liu Bo <bo.li.liu@oracle.com> wrote: > On Fri, Jul 29, 2016 at 07:01:50PM +0200, David Sterba wrote: >> On Thu, Jul 28, 2016 at 11:49:14AM -0700, Liu Bo wrote: >> > > For reviewers - this came up before here: >> > > https://patchwork.kernel.org/patch/7778651/ > > David, this patch made a mistake in commit log. > >> > > >> > > Same fix basically. >> > >> > Aha, I've given it my Reviewed-by. >> > >> > Taking either one works for me, I can make the clarifying comment into a >> > seperate patch if we need to. >> >> I'll pick the first patch and please send the separate comment update. >> Thanks. > > Sure. > > Thanks, > > -liubo > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 7a35c9d..a00fb67 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -4457,6 +4457,15 @@ void check_system_chunk(struct btrfs_trans_handle *trans, } } +/* + * If force is CHUNK_ALLOC_FORCE: + * - return 1 if it successfully allocates a chunk, + * - return errors including -ENOSPC otherwise. + * If force is NOT CHUNK_ALLOC_FORCE: + * - return 0 if it doesn't need to allocate a new chunk, + * - return 1 if it successfully allocates a chunk, + * - return errors including -ENOSPC otherwise. + */ static int do_chunk_alloc(struct btrfs_trans_handle *trans, struct btrfs_root *extent_root, u64 flags, int force) { @@ -4857,7 +4866,7 @@ static int flush_space(struct btrfs_root *root, btrfs_get_alloc_profile(root, 0), CHUNK_ALLOC_NO_FORCE); btrfs_end_transaction(trans, root); - if (ret == -ENOSPC) + if (ret == -ENOSPC || ret == 1) ret = 0; break; case COMMIT_TRANS:
Function start_transaction() can return ERR_PTR(1) when flush is BTRFS_RESERVE_FLUSH_LIMIT, so the call graph is start_transaction (return ERR_PTR(1)) -> btrfs_block_rsv_add (return 1) -> reserve_metadata_bytes (return 1) -> flush_space (return 1) -> do_chunk_alloc (return 1) With BTRFS_RESERVE_FLUSH_LIMIT, if flush_space is already on the flush_state of ALLOC_CHUNK and it successfully allocates a new chunk, then instead of trying to reserve space again, reserve_metadata_bytes returns 1 immediately. Eventually the callers who call start_transaction() usually just do the IS_ERR() check which ERR_PTR(1) can pass, then it'll get a panic when dereferencing a pointer which is ERR_PTR(1). This makes flush_space() translate 'ret = 1' to 'ret = 0'. Signed-off-by: Liu Bo <bo.li.liu@oracle.com> --- We found this 'NULL pointer dereference' on an old 3.8 kernel but it's not going to happen on the upstream since there is no caller of btrfs_start_transaction_lflush(). fs/btrfs/extent-tree.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)