Dmitry Vyukov <[email protected]> wrote:
> > Can you disassemble this function for me? There are several possible paths
> > and without the argument to the syscall and whether there's a key that was
> > matched, it's hard to say which path is being taken - but this might help
> > determine that.
>
> Here it is:
> https://gist.githubusercontent.com/dvyukov/65efc41d00ef0033f9374853b9265c71/raw/9d8540dfb199b81f3d3534ec4cc6da378d07f5b2/gistfile1.txt
Okay, it's called from here:
ffffffff820490fd: lea -0x1b0(%rbp),%rdi
ffffffff82049104: callq ffffffff82047800 <construct_get_dest_keyring>
ffffffff82049109: mov -0x1b0(%rbp),%rdi
ffffffff82049110: mov %r15,%rsi
ffffffff82049113: callq ffffffff8203efd0 <key_link> <---
ffffffff82049118: mov -0x1b0(%rbp),%rdi
ffffffff8204911f: mov %eax,%r14d
ffffffff82049122: callq ffffffff82037ab0 <key_put>
Which should correspond to this:
key_ref = search_process_keyrings(&ctx);
if (!IS_ERR(key_ref)) {
key = key_ref_to_ptr(key_ref);
if (dest_keyring) {
construct_get_dest_keyring(&dest_keyring);
ret = key_link(dest_keyring, key); <---
key_put(dest_keyring);
if (ret < 0) {
key_put(key);
key = ERR_PTR(ret);
goto error_free;
}
}
which means that the search was successful, the requested key already exists
and there was a destination keyring nominated by userspace. The first
conditional clause of construct_get_dest_keyring() must've been true:
struct key *dest_keyring = *_dest_keyring
...
if (dest_keyring) {
/* the caller supplied one */
key_get(dest_keyring);
} else {
because it matches the containing if-condition in the calling function.
> I actually know what were the arguments to the syscall. Since it
> happened in a user process context, I know what syzkaller program it
> was running at the time of the crash. It's just they are not
> reproducible. Here are the 3 programs, and they are almost equivalent
> as far as I can see. It's in syzkaller format, but I hope you can
> decipher it, it's just syscall names, address and data in hex:
> https://gist.githubusercontent.com/dvyukov/19bd59ffa286a74b49ca2371b69d4c5c/raw/004eaaa58a4ca775c008591fbb94eae78f92ef86/gistfile1.txt
add_key(&(0x7f0000d02000)="6465616400", ...
What does the "6465616400" represent? A string containing only numeric
characters or are these 2-digit hex codes and the string is actually "dead"?
David
