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author | Lennart Poettering <lennart@poettering.net> | 2023-04-13 10:21:31 +0200 |
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committer | Lennart Poettering <lennart@poettering.net> | 2023-04-13 10:21:31 +0200 |
commit | 79dec6f5cc0b72d43dfb0469fa68b5cd023fbaf9 (patch) | |
tree | 4fe1052bdd3b12837ee0bd9f942c3a4ae9e8dbd9 /src/basic/socket-util.h | |
parent | 39857544ee3794481f165e6ecc5d5a81c65f0ee9 (diff) | |
download | systemd-79dec6f5cc0b72d43dfb0469fa68b5cd023fbaf9.tar.gz |
socket-util: tighten aignment check for CMSG_TYPED_DATA()
Apparently CMSG_DATA() alignment is very much undefined. Which is quite
an ABI fuck-up, but we need to deal with this. CMSG_TYPED_DATA() already
checks alignment of the specified pointer. Let's also check matching
alignment of the underlying structures, which we already can do at
compile-time.
See: #27241
(This does not fix #27241, but should catch such errors already at
compile-time instead of runtime)
Diffstat (limited to 'src/basic/socket-util.h')
-rw-r--r-- | src/basic/socket-util.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h index 0bfb29d417..7d504319a8 100644 --- a/src/basic/socket-util.h +++ b/src/basic/socket-util.h @@ -175,9 +175,16 @@ int flush_accept(int fd); #define CMSG_FOREACH(cmsg, mh) \ for ((cmsg) = CMSG_FIRSTHDR(mh); (cmsg); (cmsg) = CMSG_NXTHDR((mh), (cmsg))) +/* Returns the cmsghdr's data pointer, but safely cast to the specified type. Does two alignment checks: one + * at compile time, that the requested type has a smaller or same alignment as 'struct cmsghdr', and one + * during runtime, that the actual pointer matches the alignment too. This is supposed to catch cases such as + * 'struct timeval' is embedded into 'struct cmsghdr' on architectures where the alignment of the former is 8 + * bytes (because of a 64bit time_t), but of the latter is 4 bytes (because size_t is 32bit), such as + * riscv32. */ #define CMSG_TYPED_DATA(cmsg, type) \ ({ \ struct cmsghdr *_cmsg = cmsg; \ + assert_cc(__alignof__(type) <= __alignof__(struct cmsghdr)); \ _cmsg ? CAST_ALIGN_PTR(type, CMSG_DATA(_cmsg)) : (type*) NULL; \ }) |