Gustavo A. R. Silva ab91c2a89f tpm: eventlog: 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] 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. Also, the following issue shows up due to the flexible-array member having incomplete type[4]: drivers/char/tpm/eventlog/tpm2.c: In function ‘tpm2_bios_measurements_start’: drivers/char/tpm/eventlog/tpm2.c:54:46: error: invalid application of ‘sizeof’ to incomplete type ‘u8[]’ {aka ‘unsigned char[]’} 54 | size = sizeof(struct tcg_pcr_event) - sizeof(event_header->event) | ^ drivers/char/tpm/eventlog/tpm2.c: In function ‘tpm2_bios_measurements_next’: drivers/char/tpm/eventlog/tpm2.c:102:10: error: invalid application of ‘sizeof’ to incomplete type ‘u8[]’ {aka ‘unsigned char[]’} 102 | sizeof(event_header->event) + event_header->event_size; | ^ drivers/char/tpm/eventlog/tpm2.c: In function ‘tpm2_binary_bios_measurements_show’: drivers/char/tpm/eventlog/tpm2.c:140:10: error: invalid application of ‘sizeof’ to incomplete type ‘u8[]’ {aka ‘unsigned char[]’} 140 | sizeof(event_header->event) + event_header->event_size; | ^ scripts/Makefile.build:266: recipe for target 'drivers/char/tpm/eventlog/tpm2.o' failed make[3]: *** [drivers/char/tpm/eventlog/tpm2.o] Error 1 As mentioned above: "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] As in "sizeof(event_header->event) always evaluated to 0, so removing it has no effect". Lastly, make use of the struct_size() helper to deal with the flexible array member and its host structure. 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 7649773293 ("cxgb3/l2t: Fix undefined behaviour") [4] https://github.com/KSPP/linux/issues/43 Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>		2020-05-22 18:50:12 +03:00
..
acpi.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
common.c	tpm: Don't make log failures fatal	2020-03-13 03:53:15 +02:00
common.h	tpm: Move eventlog declarations to its own header	2018-05-09 14:45:46 +03:00
efi.c	tpm: Don't duplicate events from the final event log in the TCG2 log	2019-06-24 23:57:50 +03:00
of.c	tpm: of: Handle IBM,vtpm20 case when getting log parameters	2020-03-13 17:31:26 +02:00
tpm1.c	tpm: tpm1_bios_measurements_next should increase position index	2020-03-13 03:53:16 +02:00
tpm2.c	tpm: eventlog: Replace zero-length array with flexible-array member	2020-05-22 18:50:12 +03:00