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| author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-27 19:14:25 +0200 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2020-06-15 14:38:56 +0200 |
| commit | 2963795122f50b36ed16e3ba880c3ed2de1bda6e (patch) | |
| tree | 352f119264084419d26025944f2a3848044788f0 /drivers/firmware | |
| parent | efivarfs: Don't return -EINTR when rate-limiting reads (diff) | |
| download | linux-2963795122f50b36ed16e3ba880c3ed2de1bda6e.tar.xz linux-2963795122f50b36ed16e3ba880c3ed2de1bda6e.zip | |
efi: Replace zero-length array and use struct_size() helper
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.
Lastly, make use of the sizeof_field() helper instead of an open-coded
version.
This issue was found with the help of Coccinelle and audited _manually_.
[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>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200527171425.GA4053@embeddedor
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Diffstat (limited to 'drivers/firmware')
| -rw-r--r-- | drivers/firmware/efi/efi.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index 7f1657b6c30d..edc5d36caf54 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -622,7 +622,8 @@ int __init efi_config_parse_tables(const efi_config_table_t *config_tables, rsv = (void *)(p + prsv % PAGE_SIZE); /* reserve the entry itself */ - memblock_reserve(prsv, EFI_MEMRESERVE_SIZE(rsv->size)); + memblock_reserve(prsv, + struct_size(rsv, entry, rsv->size)); for (i = 0; i < atomic_read(&rsv->count); i++) { memblock_reserve(rsv->entry[i].base, |