On Fri, Feb 14, 2020 at 09:43:14AM -0800, Eric Biggers wrote:
On Fri, Feb 14, 2020 at 11:24:04AM -0500, Sasha Levin wrote:From: "Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx> [ Upstream commit 987f028b8637cfa7658aa456ae73f8f21a7a7f6f ] Old code in the kernel uses 1-byte and 0-byte arrays to indicate the presence of a "variable length array": struct something { int length; u8 data[1]; }; struct something *instance; instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL); instance->length = size; memcpy(instance->data, source, size); There is also 0-byte arrays. Both cases pose confusion for things like sizeof(), CONFIG_FORTIFY_SOURCE, etc.[1] Instead, the preferred mechanism to declare variable-length types such as the one above is a flexible array member[2] which need to be the last member of a structure and empty-sized: struct something { int stuff; u8 data[]; }; Also, 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 unadvertenly introduced[3] to the codebase from now on. [1] https://github.com/KSPP/linux/issues/21 [2] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20200120235326.GA29231@xxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/char/hpet.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c index 5b38d7a8202a1..38c2ae93ce492 100644 --- a/drivers/char/hpet.c +++ b/drivers/char/hpet.c @@ -112,7 +112,7 @@ struct hpets { unsigned long hp_delta; unsigned int hp_ntimer; unsigned int hp_which; - struct hpet_dev hp_dev[1]; + struct hpet_dev hp_dev[]; };Umm, why are you backporting this without the commit that fixes it? Does your
mhm, for some reason it failed to apply to 4.19 and older. I can look at that.
AUTOSEL process really still not pay attention to Fixes tags? They are there for a reason.
Yes, it looks at the Fixes tag, thank you for the explanation.
And for that matter, why are you backporting it all, given that this is a cleanup and not a fix?
If I recall correctly CONFIG_FORTIFY_SOURCE=y results in user visible warnings, which we try to fix in the stable kernel. -- Thanks, Sasha
