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executor: disable /dev/[k]?mem access through CAP_SYS_RAWIO #6322

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executor: disable /dev/[k]?mem access through CAP_SYS_RAWIO #6322

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8 changes: 0 additions & 8 deletions dashboard/config/linux/bits/base.yml
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Expand Up @@ -190,14 +190,6 @@ config:
# We use GVNIC on Google Cloud.
- GVE: [-arm, -riscv, -s390, -timeouts_emu]

# If syzkaller gets to /dev/{mem,kmem,ioport}, it will destroy the machine.
# It managed to do so with some mount's, chdir's and bogus file names.
# These are not needed for fuzzing, so completely disabling them is
# the simplest and the most reliable option.
- DEVMEM: n
- DEVKMEM: n
- DEVPORT: n

# Disable magic SysRq completely, as it can be reached over USB and through tty.
- MAGIC_SYSRQ: n
# We don't need it and it enables MAGIC_SYSRQ and KPROBES.
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7 changes: 6 additions & 1 deletion executor/common_linux.h
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Expand Up @@ -4166,7 +4166,12 @@ static void drop_caps(void)
// which could be used to enfore safe limits without droppping CAP_SYS_NICE, but we don't have it yet.
// See the following bug for details:
// https://groups.google.com/forum/#!topic/syzkaller-bugs/G6Wl_PKPIWI
const int drop = (1 << CAP_SYS_PTRACE) | (1 << CAP_SYS_NICE);
//
// CAP_SYS_RAWIO gives direct access to various low level interfaces
// like iopl, ioperm, /proc/kcore, FIBMAP, MSRs, mmap_min_addr, pci,
// /dev/mem, /dev/kmem, low level SCSI operations, or various other
// interfaces that can directly corrupt low level kernel states.
const int drop = (1 << CAP_SYS_PTRACE) | (1 << CAP_SYS_NICE) | (1 << CAP_SYS_RAWIO);
cap_data[0].effective &= ~drop;
cap_data[0].permitted &= ~drop;
cap_data[0].inheritable &= ~drop;
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