From f490e8aea3f03497efcee81d28fd962d431663c4 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Wed, 26 Feb 2020 16:22:40 -0600 Subject: misc: Replace zero-length array with flexible-array member 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] 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 Acked-by: Dimitri Sivanich Link: https://lore.kernel.org/r/20200226222240.GA14474@embeddedor Signed-off-by: Greg Kroah-Hartman --- drivers/misc/mei/hw.h | 2 +- drivers/misc/mei/mei_dev.h | 2 +- drivers/misc/sgi-gru/grulib.h | 2 +- drivers/misc/sgi-gru/grutables.h | 2 +- 4 files changed, 4 insertions(+), 4 deletions(-) (limited to 'drivers/misc') diff --git a/drivers/misc/mei/hw.h b/drivers/misc/mei/hw.h index 8231b6941adf..b1a8d5ec88b3 100644 --- a/drivers/misc/mei/hw.h +++ b/drivers/misc/mei/hw.h @@ -216,7 +216,7 @@ struct mei_msg_hdr { struct mei_bus_message { u8 hbm_cmd; - u8 data[0]; + u8 data[]; } __packed; /** diff --git a/drivers/misc/mei/mei_dev.h b/drivers/misc/mei/mei_dev.h index 76f8ff5ff974..3a29db07211d 100644 --- a/drivers/misc/mei/mei_dev.h +++ b/drivers/misc/mei/mei_dev.h @@ -533,7 +533,7 @@ struct mei_device { #endif /* CONFIG_DEBUG_FS */ const struct mei_hw_ops *ops; - char hw[0] __aligned(sizeof(void *)); + char hw[] __aligned(sizeof(void *)); }; static inline unsigned long mei_secs_to_jiffies(unsigned long sec) diff --git a/drivers/misc/sgi-gru/grulib.h b/drivers/misc/sgi-gru/grulib.h index e77d1b1f9d05..85c103923632 100644 --- a/drivers/misc/sgi-gru/grulib.h +++ b/drivers/misc/sgi-gru/grulib.h @@ -136,7 +136,7 @@ struct gru_dump_context_header { pid_t pid; unsigned long vaddr; int cch_locked; - unsigned long data[0]; + unsigned long data[]; }; /* diff --git a/drivers/misc/sgi-gru/grutables.h b/drivers/misc/sgi-gru/grutables.h index a7e44b2eb413..5ce8f3081e96 100644 --- a/drivers/misc/sgi-gru/grutables.h +++ b/drivers/misc/sgi-gru/grutables.h @@ -372,7 +372,7 @@ struct gru_thread_state { int ts_data_valid; /* Indicates if ts_gdata has valid data */ struct gru_gseg_statistics ustats; /* User statistics */ - unsigned long ts_gdata[0]; /* save area for GRU data (CB, + unsigned long ts_gdata[]; /* save area for GRU data (CB, DS, CBE) */ }; -- cgit v1.2.3