From 8128d3aac0ee3420ede34950c9c0ef9ee118bec9 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 9 Mar 2020 15:23:27 -0500 Subject: pstore/ram: 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 Link: https://lore.kernel.org/r/20200309202327.GA8813@embeddedor Signed-off-by: Kees Cook --- fs/pstore/ram_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/pstore') diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c index 1f4d8c06f9be..c917c191e78c 100644 --- a/fs/pstore/ram_core.c +++ b/fs/pstore/ram_core.c @@ -34,7 +34,7 @@ struct persistent_ram_buffer { uint32_t sig; atomic_t start; atomic_t size; - uint8_t data[0]; + uint8_t data[]; }; #define PERSISTENT_RAM_SIG (0x43474244) /* DBGC */ -- cgit