| Message ID | 156622692131.21558.12335114959426121841.stgit@warthog.procyon.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | keys: Fix description size | expand |
On Mon, Aug 19, 2019 at 8:02 AM David Howells <dhowells@redhat.com> wrote: > > This can be fixed by simply increasing the size of desc_len in struct > keyring_index_key to a u16. Thanks, applied. Linus
diff --git a/include/linux/key.h b/include/linux/key.h index 91f391cd272e..50028338a4cc 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -94,11 +94,11 @@ struct keyring_index_key { union { struct { #ifdef __LITTLE_ENDIAN /* Put desc_len at the LSB of x */ - u8 desc_len; - char desc[sizeof(long) - 1]; /* First few chars of description */ + u16 desc_len; + char desc[sizeof(long) - 2]; /* First few chars of description */ #else - char desc[sizeof(long) - 1]; /* First few chars of description */ - u8 desc_len; + char desc[sizeof(long) - 2]; /* First few chars of description */ + u16 desc_len; #endif }; unsigned long x;
The maximum key description size is 4095. Commit f771fde82051 inadvertantly reduced that to 255 and made sizes between 256 and 4095 work weirdly, and any size whereby size & 255 == 0 would cause an assertion in __key_link_begin() at the following line: BUG_ON(index_key->desc_len == 0); This can be fixed by simply increasing the size of desc_len in struct keyring_index_key to a u16. Note the argument length test in keyutils only checked empty descriptions and descriptions with a size around the limit (ie. 4095) and not for all the values in between, so it missed this. This has been addressed and https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git/commit/?id=066bf56807c26cd3045a25f355b34c1d8a20a5aa now exhaustively tests all possible lengths of type, description and payload and then some. The assertion failure looks something like: kernel BUG at security/keys/keyring.c:1245! ... RIP: 0010:__key_link_begin+0x88/0xa0 ... Call Trace: key_create_or_update+0x211/0x4b0 __x64_sys_add_key+0x101/0x200 do_syscall_64+0x5b/0x1e0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 It can be triggered by: keyctl add user "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" a @s Fixes: f771fde82051 ("keys: Simplify key description management") Reported-by: kernel test robot <rong.a.chen@intel.com> Signed-off-by: David Howells <dhowells@redhat.com> cc: Linus Torvalds <torvalds@linux-foundation.org> --- include/linux/key.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)