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The Linux 5.16.14 kernel's coccicheck caught this. The semantic
patch that caught it was:
./scripts/coccinelle/misc/flexible_array.cocci
However, unlike the cases where the GNU zero length array extension had
been used, coccicheck would not suggest patches for the older style
single member arrays. That was good because blindly changing them would
break size calculations in most cases.
Therefore, this required care to make sure that we did not break size
calculations. In the case of `indirect_split_t`, we use
`offsetof(indirect_split_t, is_child[is->is_children])` to calculate
size. This might be subtly wrong according to an old mailing list
thread:
https://inbox.sourceware.org/gcc-prs/[email protected]/T/
That is because the C99 specification should consider the flexible array
members to start at the end of a structure, but compilers prefer to put
padding at the end. A suggestion was made to allow compilers to allocate
padding after the VLA like compilers already did:
http://std.dkuug.dk/JTC1/SC22/WG14/www/docs/n983.htm
However, upon thinking about it, whether or not we allocate end of
structure padding does not matter, so using offsetof() to calculate the
size of the structure is fine, so long as we do not mix it with sizeof()
on structures with no array members.
In the case that we mix them and padding causes offsetof(struct_t,
vla_member[0]) to differ from sizeof(struct_t), we would be doing unsafe
operations if we underallocate via `offsetof()` and then overcopy via
sizeof().
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Richard Yao <[email protected]>
Closes #14372
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69 CSTYLED BEGINs remain, appx. 30 of which can be removed if cstyle(1)
had a useful policy regarding
CALL(ARG1,
ARG2,
ARG3);
above 2 lines. As it stands, it spits out *both*
sysctl_os.c: 385: continuation line should be indented by 4 spaces
sysctl_os.c: 385: indent by spaces instead of tabs
which is very cool
Another >10 could be fixed by removing "ulong" &al. handling.
I don't foresee anyone actually using it intentionally
(does it even exist in modern headers? why did it in the first place?).
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Ahelenia Ziemiańska <[email protected]>
Closes #12993
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