diff options
| author | Aleksandr Nogikh <nogikh@google.com> | 2022-01-12 14:40:51 +0000 |
|---|---|---|
| committer | Aleksandr Nogikh <wp32pw@gmail.com> | 2022-01-13 17:03:14 +0100 |
| commit | d6f3385b1a3f2fba8e14d6794bece1dcdd9e479e (patch) | |
| tree | c3163643d321b913450df84f41731b71d5874243 /sys/linux/sys.txt | |
| parent | 6baa7baec59a790c452b0b1c97447475eb6c1afe (diff) | |
all: add syz_clone() and syz_clone3() pseudo calls
As was pointed out in #2921, the current approach of limiting the number
of pids per process does not work on all Linux-based kernels.
We could just treat fork, clone and clone3 in a special way (e.g. exit
on a zero return). However, in that case we also need to sanitize the
arguments for clone and clone3 - if CLONE_VM is passed and stack is 0,
the forked child processes (threads) will become nearly unindentifiable
and will corrupt syz-executor's memory. While we could sanitize clone's
arguments, we cannot do so for clone3 - nothing can guarantee that they
will not be changed concurrently.
Instead of calling those syscalls directly, introduce a special pseudo
syscall syz_clone3. It copies and sanitizes the arguments and then
executes clone3 (or fork, if we're on an older kernel) in such a way so
as to prevent fork bombs from happening.
Also introduce syz_clone() to still be able to fuzz it on older systems.
Diffstat (limited to 'sys/linux/sys.txt')
| -rw-r--r-- | sys/linux/sys.txt | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/sys/linux/sys.txt b/sys/linux/sys.txt index fd934f976..8664e09a8 100644 --- a/sys/linux/sys.txt +++ b/sys/linux/sys.txt @@ -293,9 +293,14 @@ utimes(filename ptr[in, filename], times ptr[in, itimerval]) futimesat(dir fd_dir, pathname ptr[in, filename], times ptr[in, itimerval]) utimensat(dir fd_dir, pathname ptr[in, filename], times ptr[in, itimerval], flags flags[utimensat_flags]) -fork() pid (breaks_returns) -clone(flags flags[clone_flags], sp buffer[in], parentid ptr[out, int32], childtid ptr[out, int32], tls buffer[in]) (breaks_returns) -clone3(args ptr[in, clone_args], size bytesize[args]) pid (breaks_returns) +# Small trick - syzkaller cannot give the proper stack pointer to clone(), but we can do it with the aid of pseudo syscalls. +syz_clone(flags flags[clone_flags], stack buffer[in], stack_len bytesize[stack], parentid ptr[out, int32], childtid ptr[out, int32], tls buffer[in]) pid + +syz_clone3(args ptr[in, clone_args], size bytesize[args]) pid + +# We need these disabled definitions to simplify the presence and the NR checking. +clone(flags flags[clone_flags], sp buffer[in], parentid ptr[out, int32], childtid ptr[out, int32], tls buffer[in]) (breaks_returns, disabled) +clone3(args ptr[in, clone_args], size bytesize[args]) pid (breaks_returns, disabled) clone_args { flags flags[clone3_flags, int64] |