Messages in this thread | | | From | Ard Biesheuvel <> | Date | Wed, 8 Jun 2022 10:24:23 +0200 | Subject | Re: [PATCH] random: do not use jump labels before they are initialized |
| |
On Tue, 7 Jun 2022 at 12:04, Jason A. Donenfeld <Jason@zx2c4.com> wrote: > > [ I would like to pursue fixing this more directly first before actually > merging this, but I thought I'd send this to the list now anyway as a > the "backup" plan. If I can't figure out how to make headway on the > main plan in the next few days, it'll be easy to just do this. ] > > Stephen reported that a static key warning splat appears during early > boot on systems that credit randomness from device trees that contain an > "rng-seed" property, because because setup_machine_fdt() is called > before jump_label_init() during setup_arch(): > > static_key_enable_cpuslocked(): static key '0xffffffe51c6fcfc0' used before call to jump_label_init() > WARNING: CPU: 0 PID: 0 at kernel/jump_label.c:166 static_key_enable_cpuslocked+0xb0/0xb8 > Modules linked in: > CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0+ #224 44b43e377bfc84bc99bb5ab885ff694984ee09ff > pstate: 600001c9 (nZCv dAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : static_key_enable_cpuslocked+0xb0/0xb8 > lr : static_key_enable_cpuslocked+0xb0/0xb8 > sp : ffffffe51c393cf0 > x29: ffffffe51c393cf0 x28: 000000008185054c x27: 00000000f1042f10 > x26: 0000000000000000 x25: 00000000f10302b2 x24: 0000002513200000 > x23: 0000002513200000 x22: ffffffe51c1c9000 x21: fffffffdfdc00000 > x20: ffffffe51c2f0831 x19: ffffffe51c6fcfc0 x18: 00000000ffff1020 > x17: 00000000e1e2ac90 x16: 00000000000000e0 x15: ffffffe51b710708 > x14: 0000000000000066 x13: 0000000000000018 x12: 0000000000000000 > x11: 0000000000000000 x10: 00000000ffffffff x9 : 0000000000000000 > x8 : 0000000000000000 x7 : 61632065726f6665 x6 : 6220646573752027 > x5 : ffffffe51c641d25 x4 : ffffffe51c13142c x3 : ffff0a00ffffff05 > x2 : 40000000ffffe003 x1 : 00000000000001c0 x0 : 0000000000000065 > Call trace: > static_key_enable_cpuslocked+0xb0/0xb8 > static_key_enable+0x2c/0x40 > crng_set_ready+0x24/0x30 > execute_in_process_context+0x80/0x90 > _credit_init_bits+0x100/0x154 > add_bootloader_randomness+0x64/0x78 > early_init_dt_scan_chosen+0x140/0x184 > early_init_dt_scan_nodes+0x28/0x4c > early_init_dt_scan+0x40/0x44 > setup_machine_fdt+0x7c/0x120 > setup_arch+0x74/0x1d8 > start_kernel+0x84/0x44c > __primary_switched+0xc0/0xc8 > ---[ end trace 0000000000000000 ]--- > random: crng init done > Machine model: Google Lazor (rev1 - 2) with LTE > > A trivial fix went in to address this on arm64, 73e2d827a501 ("arm64: > Initialize jump labels before setup_machine_fdt()"). But it appears that > fixing it on other platforms might not be so trivial. Instead, defer the > setting of the static branch until later in the boot process. > > Fixes: f5bda35fba61 ("random: use static branch for crng_ready()") > Reported-by: Stephen Boyd <swboyd@chromium.org> > Cc: Ard Biesheuvel <ardb@kernel.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Russell King <linux@armlinux.org.uk> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Phil Elwell <phil@raspberrypi.com> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
> --- > drivers/char/random.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/drivers/char/random.c b/drivers/char/random.c > index 4862d4d3ec49..f9a020ec08b9 100644 > --- a/drivers/char/random.c > +++ b/drivers/char/random.c > @@ -650,7 +650,8 @@ static void __cold _credit_init_bits(size_t bits) > > if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) { > crng_reseed(); /* Sets crng_init to CRNG_READY under base_crng.lock. */ > - execute_in_process_context(crng_set_ready, &set_ready); > + if (static_key_initialized) > + execute_in_process_context(crng_set_ready, &set_ready); > wake_up_interruptible(&crng_init_wait); > kill_fasync(&fasync, SIGIO, POLL_IN); > pr_notice("crng init done\n"); > @@ -779,6 +780,14 @@ int __init random_init(const char *command_line) > unsigned int i, arch_bytes; > unsigned long entropy; > > + /* > + * If we were initialized by the bootloader before jump labels are > + * initialized, then we should enable the static branch here, where > + * it's guaranteed that jump labels have been initialized. > + */ > + if (!static_branch_likely(&crng_is_ready) && crng_init >= CRNG_READY) > + crng_set_ready(NULL); > + > #if defined(LATENT_ENTROPY_PLUGIN) > static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy; > _mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed)); > -- > 2.35.1 >
| |