From 00b42b70ae521e6ccc86ed403e2d101616689bdc Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 7 May 2020 14:21:47 -0500 Subject: scsi: libsas: Replace zero-length array with flexible-array 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") Link: https://lore.kernel.org/r/20200507192147.GA16206@embeddedor Reviewed-by: John Garry Reviewed-by: Jason Yan Signed-off-by: Gustavo A. R. Silva Signed-off-by: Martin K. Petersen --- include/scsi/sas.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'include/scsi/sas.h') 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 { -- cgit v1.2.3