Messages in this thread Patch in this message | | | Date | Thu, 7 May 2020 14:27:12 -0500 | From | "Gustavo A. R. Silva" <> | Subject | [PATCH] efi: Replace zero-length array with flexible-array |
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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> --- include/linux/dma/ti-cppi5.h | 4 ++-- include/linux/efi.h | 2 +- include/linux/mailbox/zynqmp-ipi-message.h | 2 +- include/linux/platform_data/cros_ec_commands.h | 4 ++-- include/linux/platform_data/cros_ec_proto.h | 2 +- kernel/params.c | 2 +- kernel/tracepoint.c | 2 +- scripts/kallsyms.c | 2 +- 8 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/include/linux/dma/ti-cppi5.h b/include/linux/dma/ti-cppi5.h index 579356ae447e..78c911269107 100644 --- a/include/linux/dma/ti-cppi5.h +++ b/include/linux/dma/ti-cppi5.h @@ -47,7 +47,7 @@ struct cppi5_host_desc_t { u32 buf_info1; u32 org_buf_len; u64 org_buf_ptr; - u32 epib[0]; + u32 epib[]; } __packed; #define CPPI5_DESC_MIN_ALIGN (16U) @@ -139,7 +139,7 @@ struct cppi5_desc_epib_t { */ struct cppi5_monolithic_desc_t { struct cppi5_desc_hdr_t hdr; - u32 epib[0]; + u32 epib[]; }; #define CPPI5_INFO2_MDESC_DATA_OFFSET_SHIFT (18U) diff --git a/include/linux/efi.h b/include/linux/efi.h index 251f1f783cdf..a657850899f0 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1234,7 +1234,7 @@ struct linux_efi_memreserve { struct { phys_addr_t base; phys_addr_t size; - } entry[0]; + } entry[]; }; #define EFI_MEMRESERVE_SIZE(count) (sizeof(struct linux_efi_memreserve) + \ diff --git a/include/linux/mailbox/zynqmp-ipi-message.h b/include/linux/mailbox/zynqmp-ipi-message.h index 9542b41eacfd..35ce84c8ca02 100644 --- a/include/linux/mailbox/zynqmp-ipi-message.h +++ b/include/linux/mailbox/zynqmp-ipi-message.h @@ -14,7 +14,7 @@ */ struct zynqmp_ipi_message { size_t len; - u8 data[0]; + u8 data[]; }; #endif /* _LINUX_ZYNQMP_IPI_MESSAGE_H_ */ diff --git a/include/linux/platform_data/cros_ec_commands.h b/include/linux/platform_data/cros_ec_commands.h index 69210881ebac..451885c697cc 100644 --- a/include/linux/platform_data/cros_ec_commands.h +++ b/include/linux/platform_data/cros_ec_commands.h @@ -5065,7 +5065,7 @@ struct ec_response_pd_log { uint8_t type; /* event type : see PD_EVENT_xx below */ uint8_t size_port; /* [7:5] port number [4:0] payload size in bytes */ uint16_t data; /* type-defined data payload */ - uint8_t payload[0]; /* optional additional data payload: 0..16 bytes */ + uint8_t payload[]; /* optional additional data payload: 0..16 bytes */ } __ec_align4; /* The timestamp is the microsecond counter shifted to get about a ms. */ @@ -5691,7 +5691,7 @@ struct ec_response_fp_encryption_status { struct ec_response_tp_frame_info { uint32_t n_frames; - uint32_t frame_sizes[0]; + uint32_t frame_sizes[]; } __ec_align4; /* Create a snapshot of current frame readings */ diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h index 383243326676..7f03e02c48cd 100644 --- a/include/linux/platform_data/cros_ec_proto.h +++ b/include/linux/platform_data/cros_ec_proto.h @@ -69,7 +69,7 @@ struct cros_ec_command { uint32_t outsize; uint32_t insize; uint32_t result; - uint8_t data[0]; + uint8_t data[]; }; /** diff --git a/kernel/params.c b/kernel/params.c index 8e56f8b12d8f..55c07e3b9903 100644 --- a/kernel/params.c +++ b/kernel/params.c @@ -529,7 +529,7 @@ struct module_param_attrs { unsigned int num; struct attribute_group grp; - struct param_attribute attrs[0]; + struct param_attribute attrs[]; }; #ifdef CONFIG_SYSFS diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 73956eaff8a9..3ee46cda2692 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -50,7 +50,7 @@ static bool ok_to_free_tracepoints; */ struct tp_probes { struct rcu_head rcu; - struct tracepoint_func probes[0]; + struct tracepoint_func probes[]; }; static inline void *allocate_probes(int count) diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c index 3e8dea6e0a95..6dc3078649fa 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -34,7 +34,7 @@ struct sym_entry { unsigned int len; unsigned int start_pos; unsigned int percpu_absolute; - unsigned char sym[0]; + unsigned char sym[]; }; struct addr_range {
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