Hi Romain, On Tue, 2024-06-25 at 10:22 +0200, Romain Naour wrote: > Hello, > > I'm using the kernel 6.1.80-ti-arm64-r50 provided by Debian Bullseye image for > the beaglebone-ai-64 [1] (the same happen with a Yocto/Buildroot based image > with the latest 6.9.x vanilla kernel) > > $ uname -a > Linux BeagleBone 6.1.80-ti-arm64-r50 #1 bullseye SMP PREEMPT_DYNAMIC Fri May > 24 19:44:30 UTC 2024 aarch64 GNU/Linux > > But I noticed that the i2c bus is probed after the IMA/EVM infra. > What if a TPM is connected by i2c bus ? > > [ 1.306865] ima: No TPM chip found, activating TPM-bypass! > ... > [ 1.370601] ti-sci 44083000.system-controller: ABI: 3.1 (firmware rev 0x0015 > '21.5.0--v2021.05 (Terrific Llam') > [ 1.428399] omap_i2c 42120000.i2c: bus 0 rev0.12 at 400 kHz > [ 1.434666] omap_i2c 2000000.i2c: bus 4 rev0.12 at 400 kHz > [ 1.440738] omap_i2c 2010000.i2c: bus 5 rev0.12 at 400 kHz > [ 1.446798] omap_i2c 2020000.i2c: bus 2 rev0.12 at 100 kHz > [ 1.452907] omap_i2c 2030000.i2c: bus 6 rev0.12 at 400 kHz > [ 1.458983] omap_i2c 2040000.i2c: bus 3 rev0.12 at 100 kHz > [ 1.465082] omap_i2c 2050000.i2c: bus 7 rev0.12 at 400 kHz > [ 1.471146] omap_i2c 2060000.i2c: bus 1 rev0.12 at 100 kHz > > I'm not sure this issue is really specific to the board, there were a similar > issue on rpi board: > > https://github.com/Cybersecurity-LINKS/tpm-ima-patch > > After digging into this problem, I did two changes to ima/evm driver to replace > late_initcall() by late_initcall_sync() > (Tested on a vanilla 6.6.33 kernel) > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > index ff9a939dad8e..339f6e8d7e56 100644 > --- a/security/integrity/evm/evm_main.c > +++ b/security/integrity/evm/evm_main.c > @@ -960,4 +960,4 @@ static int __init init_evm(void) > return error; > } > > -late_initcall(init_evm); > +late_initcall_sync(init_evm); /* Start EVM after the IMA */ > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c > index cc1217ac2c6f..1e9417ffdf08 100644 > --- a/security/integrity/ima/ima_main.c > +++ b/security/integrity/ima/ima_main.c > @@ -1120,4 +1120,4 @@ static int __init init_ima(void) > return error; > } > > -late_initcall(init_ima); /* Start IMA after the TPM is available */ > +late_initcall_sync(init_ima); /* Start IMA after the TPM is available */ > > Now, the IMA/EVM stack are initialized *after* the TPM device. > > [ 0.285986] omap_i2c 42120000.i2c: bus 0 rev0.12 at 400 kHz > [ 0.286706] omap_i2c 2000000.i2c: bus 4 rev0.12 at 400 kHz > [ 0.287382] omap_i2c 2010000.i2c: bus 5 rev0.12 at 400 kHz > [ 0.331503] tpm_tis_i2c 2-002e: 2.0 TPM (device-id 0x1C, rev-id 22) > [ 0.677185] omap_i2c 2020000.i2c: bus 2 rev0.12 at 100 kHz > [ 0.677904] omap_i2c 2030000.i2c: bus 6 rev0.12 at 400 kHz > [ 0.678557] omap_i2c 2040000.i2c: bus 3 rev0.12 at 100 kHz > [ 0.679167] omap_i2c 2050000.i2c: bus 7 rev0.12 at 400 kHz > [ 0.679792] omap_i2c 2060000.i2c: bus 1 rev0.12 at 100 kHz > > [ 3.062788] ima: Allocated hash algorithm: sha256 > > [ 3.318975] ima: No architecture policies found > [ 3.323536] evm: Initialising EVM extended attributes: > [ 3.328662] evm: security.selinux (disabled) > [ 3.332919] evm: security.SMACK64 (disabled) > [ 3.337177] evm: security.SMACK64EXEC (disabled) > [ 3.341781] evm: security.SMACK64TRANSMUTE (disabled) > [ 3.346819] evm: security.SMACK64MMAP (disabled) > [ 3.351422] evm: security.apparmor (disabled) > [ 3.355764] evm: security.ima > [ 3.358721] evm: security.capability > [ 3.362285] evm: HMAC attrs: 0x1 > > Thoughts? > > Initially reported on TI forum and Beaglebord Discord [2] > > [1]: https://www.beagleboard.org/boards/beaglebone-ai-64 > [2]: > https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1375425/tda4vm-ima-vs-tpm-builtin-driver-boot-order As long as IMA (and EVM) are initialized before accessing files from real root or loading kernel modules, I don't have a problem with moving it to late_initcall_sync(). Please post the IMA and EVM patches here on the linux-integrity mailing list. thanks, Mimi
