| Message ID | 20200507192147.GA16206@embeddedor (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 00b42b70ae521e6ccc86ed403e2d101616689bdc |
| Headers | show |
| Series | scsi: libsas: Replace zero-length array with flexible-array | expand |
On 07/05/2020 20:21, Gustavo A. R. Silva wrote: > The current codebase makes use of the zero-length array language > extension to the C90 standard, but the preferred mechanism to declare > variable-length types such as these ones is a flexible array member[1][2], > introduced in C99: > > struct foo { > int stuff; > struct boo array[]; > }; > > By making use of the mechanism above, we will get a compiler warning > in case the flexible array does not occur last in the structure, which > will help us prevent some kind of undefined behavior bugs from being > inadvertently introduced[3] to the codebase from now on. > > Also, notice that, dynamic memory allocations won't be affected by > this change: > > "Flexible array members have incomplete type, and so the sizeof operator > may not be applied. As a quirk of the original implementation of > zero-length arrays, sizeof evaluates to zero."[1] > > sizeof(flexible-array-member) triggers a warning because flexible array > members have incomplete type[1]. There are some instances of code in > which the sizeof operator is being incorrectly/erroneously applied to > zero-length arrays and the result is zero. Such instances may be hiding > some bugs. So, this work (flexible-array member conversions) will also > help to get completely rid of those sorts of issues. > > This issue was found with the help of Coccinelle. > > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html > [2] https://github.com/KSPP/linux/issues/21 > [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") > > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Reviewed-by: John Garry <john.garry@huawei.com> > --- > drivers/scsi/aic94xx/aic94xx_sds.c | 14 +++++++------- > include/scsi/sas.h | 8 ++++---- > 2 files changed, 11 insertions(+), 11 deletions(-) > > diff --git a/drivers/scsi/aic94xx/aic94xx_sds.c b/drivers/scsi/aic94xx/aic94xx_sds.c > index 3ddc8852bc32..105adba559a1 100644 > --- a/drivers/scsi/aic94xx/aic94xx_sds.c > +++ b/drivers/scsi/aic94xx/aic94xx_sds.c > @@ -406,7 +406,7 @@ struct asd_manuf_sec { > u8 sas_addr[SAS_ADDR_SIZE]; > u8 pcba_sn[ASD_PCBA_SN_SIZE]; > /* Here start the other segments */ > - u8 linked_list[0]; > + u8 linked_list[]; > } __attribute__ ((packed)); > > struct asd_manuf_phy_desc { > @@ -449,7 +449,7 @@ struct asd_ms_sb_desc { > u8 type; > u8 node_desc_index; > u8 conn_desc_index; > - u8 _recvd[0]; > + u8 _recvd[]; > } __attribute__ ((packed)); > > #if 0 > @@ -478,12 +478,12 @@ struct asd_ms_conn_desc { > u8 size_sideband_desc; > u32 _resvd; > u8 name[16]; > - struct asd_ms_sb_desc sb_desc[0]; > + struct asd_ms_sb_desc sb_desc[]; > } __attribute__ ((packed)); > > struct asd_nd_phy_desc { > u8 vp_attch_type; > - u8 attch_specific[0]; > + u8 attch_specific[]; > } __attribute__ ((packed)); > > #if 0 > @@ -503,7 +503,7 @@ struct asd_ms_node_desc { > u8 size_phy_desc; > u8 _resvd; > u8 name[16]; > - struct asd_nd_phy_desc phy_desc[0]; > + struct asd_nd_phy_desc phy_desc[]; > } __attribute__ ((packed)); > > struct asd_ms_conn_map { > @@ -518,7 +518,7 @@ struct asd_ms_conn_map { > u8 usage_model_id; > u32 _resvd; > struct asd_ms_conn_desc conn_desc[0]; > - struct asd_ms_node_desc node_desc[0]; > + struct asd_ms_node_desc node_desc[]; > } __attribute__ ((packed)); > > struct asd_ctrla_phy_entry { > @@ -542,7 +542,7 @@ struct asd_ll_el { > u8 id0; > u8 id1; > __le16 next; > - u8 something_here[0]; > + u8 something_here[]; > } __attribute__ ((packed)); > > static int asd_poll_flash(struct asd_ha_struct *asd_ha) > diff --git a/include/scsi/sas.h b/include/scsi/sas.h > index a5d8ae49198c..4726c1bbec65 100644 > --- a/include/scsi/sas.h > +++ b/include/scsi/sas.h > @@ -324,7 +324,7 @@ struct ssp_response_iu { > __be32 response_data_len; > > u8 resp_data[0]; JFYI, We still have a zero-length array here, and some ideas to remove it are here: https://lore.kernel.org/linux-scsi/CAK8P3a1=5dmgB+k9B_jk2qBhBPnMSFMWrByP4jRvyvaJwBo94A@mail.gmail.com/ > - u8 sense_data[0]; > + u8 sense_data[]; > } __attribute__ ((packed)); > > struct ssp_command_iu { > @@ -346,7 +346,7 @@ struct ssp_command_iu { > u8 add_cdb_len:6; > > u8 cdb[16]; > - u8 add_cdb[0]; > + u8 add_cdb[]; > } __attribute__ ((packed)); > > struct xfer_rdy_iu { > @@ -555,7 +555,7 @@ struct ssp_response_iu { > __be32 response_data_len; > > u8 resp_data[0]; > - u8 sense_data[0]; > + u8 sense_data[]; > } __attribute__ ((packed)); > > struct ssp_command_iu { > @@ -577,7 +577,7 @@ struct ssp_command_iu { > u8 _r_c:2; > > u8 cdb[16]; > - u8 add_cdb[0]; > + u8 add_cdb[]; > } __attribute__ ((packed)); > > struct xfer_rdy_iu { > > . >
在 2020/5/8 3:21, Gustavo A. R. Silva 写道: > The current codebase makes use of the zero-length array language > extension to the C90 standard, but the preferred mechanism to declare > variable-length types such as these ones is a flexible array member[1][2], > introduced in C99: > > struct foo { > int stuff; > struct boo array[]; > }; > > By making use of the mechanism above, we will get a compiler warning > in case the flexible array does not occur last in the structure, which > will help us prevent some kind of undefined behavior bugs from being > inadvertently introduced[3] to the codebase from now on. > > Also, notice that, dynamic memory allocations won't be affected by > this change: > > "Flexible array members have incomplete type, and so the sizeof operator > may not be applied. As a quirk of the original implementation of > zero-length arrays, sizeof evaluates to zero."[1] > > sizeof(flexible-array-member) triggers a warning because flexible array > members have incomplete type[1]. There are some instances of code in > which the sizeof operator is being incorrectly/erroneously applied to > zero-length arrays and the result is zero. Such instances may be hiding > some bugs. So, this work (flexible-array member conversions) will also > help to get completely rid of those sorts of issues. > > This issue was found with the help of Coccinelle. > > [1]https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html > [2]https://github.com/KSPP/linux/issues/21 > [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") > > Signed-off-by: Gustavo A. R. Silva<gustavoars@kernel.org> Reviewed-by: Jason Yan <yanaijie@huawei.com>
On Thu, 7 May 2020 14:21:47 -0500, Gustavo A. R. Silva wrote: > The current codebase makes use of the zero-length array language > extension to the C90 standard, but the preferred mechanism to declare > variable-length types such as these ones is a flexible array member[1][2], > introduced in C99: > > struct foo { > int stuff; > struct boo array[]; > }; > > [...] Applied to 5.8/scsi-queue, thanks! [1/1] scsi: libsas: Replace zero-length array with flexible-array https://git.kernel.org/mkp/scsi/c/00b42b70ae52
diff --git a/drivers/scsi/aic94xx/aic94xx_sds.c b/drivers/scsi/aic94xx/aic94xx_sds.c index 3ddc8852bc32..105adba559a1 100644 --- a/drivers/scsi/aic94xx/aic94xx_sds.c +++ b/drivers/scsi/aic94xx/aic94xx_sds.c @@ -406,7 +406,7 @@ struct asd_manuf_sec { u8 sas_addr[SAS_ADDR_SIZE]; u8 pcba_sn[ASD_PCBA_SN_SIZE]; /* Here start the other segments */ - u8 linked_list[0]; + u8 linked_list[]; } __attribute__ ((packed)); struct asd_manuf_phy_desc { @@ -449,7 +449,7 @@ struct asd_ms_sb_desc { u8 type; u8 node_desc_index; u8 conn_desc_index; - u8 _recvd[0]; + u8 _recvd[]; } __attribute__ ((packed)); #if 0 @@ -478,12 +478,12 @@ struct asd_ms_conn_desc { u8 size_sideband_desc; u32 _resvd; u8 name[16]; - struct asd_ms_sb_desc sb_desc[0]; + struct asd_ms_sb_desc sb_desc[]; } __attribute__ ((packed)); struct asd_nd_phy_desc { u8 vp_attch_type; - u8 attch_specific[0]; + u8 attch_specific[]; } __attribute__ ((packed)); #if 0 @@ -503,7 +503,7 @@ struct asd_ms_node_desc { u8 size_phy_desc; u8 _resvd; u8 name[16]; - struct asd_nd_phy_desc phy_desc[0]; + struct asd_nd_phy_desc phy_desc[]; } __attribute__ ((packed)); struct asd_ms_conn_map { @@ -518,7 +518,7 @@ struct asd_ms_conn_map { u8 usage_model_id; u32 _resvd; struct asd_ms_conn_desc conn_desc[0]; - struct asd_ms_node_desc node_desc[0]; + struct asd_ms_node_desc node_desc[]; } __attribute__ ((packed)); struct asd_ctrla_phy_entry { @@ -542,7 +542,7 @@ struct asd_ll_el { u8 id0; u8 id1; __le16 next; - u8 something_here[0]; + u8 something_here[]; } __attribute__ ((packed)); static int asd_poll_flash(struct asd_ha_struct *asd_ha) diff --git a/include/scsi/sas.h b/include/scsi/sas.h index a5d8ae49198c..4726c1bbec65 100644 --- a/include/scsi/sas.h +++ b/include/scsi/sas.h @@ -324,7 +324,7 @@ struct ssp_response_iu { __be32 response_data_len; u8 resp_data[0]; - u8 sense_data[0]; + u8 sense_data[]; } __attribute__ ((packed)); struct ssp_command_iu { @@ -346,7 +346,7 @@ struct ssp_command_iu { u8 add_cdb_len:6; u8 cdb[16]; - u8 add_cdb[0]; + u8 add_cdb[]; } __attribute__ ((packed)); struct xfer_rdy_iu { @@ -555,7 +555,7 @@ struct ssp_response_iu { __be32 response_data_len; u8 resp_data[0]; - u8 sense_data[0]; + u8 sense_data[]; } __attribute__ ((packed)); struct ssp_command_iu { @@ -577,7 +577,7 @@ struct ssp_command_iu { u8 _r_c:2; u8 cdb[16]; - u8 add_cdb[0]; + u8 add_cdb[]; } __attribute__ ((packed)); struct xfer_rdy_iu {
The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- drivers/scsi/aic94xx/aic94xx_sds.c | 14 +++++++------- include/scsi/sas.h | 8 ++++---- 2 files changed, 11 insertions(+), 11 deletions(-)