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pid1: stop making /dev noexec

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Quoting Andy Lutomirski:
> The upcoming Linux SGX driver has a device node /dev/sgx.  User code opens
> it, does various setup things, mmaps it, and needs to be able to create
> PROT_EXEC mappings.  This gets quite awkward if /dev is mounted noexec.

We already didn't use noexec in spawn, and this extends this behaviour to other
systems.

Afaik, the kernel would refuse execve() on a character or block device
anyway. Thus noexec on /dev matters only for actual binaries copied to /dev,
which requires root privileges in the first place.

We don't do noexec on either /tmp or /dev/shm (because that causes immediate
problems with stuff like Java and cffi). And if you have those two at your
disposal anyway, having noexec on /dev doesn't seem important. So the 'noexec'
attribute on /dev doesn't really mean much, since there are multiple other
similar directories which don't require root privileges to write to.

C.f. 33c10ef43b.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2020-12-11 12:28:44 +01:00 committed by Luca Boccassi
parent 25b514cd00
commit 4eb105fa4a
1 changed files with 1 additions and 1 deletions
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2
src/core/mount-setup.c
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@ -66,7 +66,7 @@ static const MountPoint mount_table[] = {
NULL, MNT_FATAL|MNT_IN_CONTAINER|MNT_FOLLOW_SYMLINK },
{ "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "devtmpfs", "/dev", "devtmpfs", "mode=755" TMPFS_LIMITS_DEV, MS_NOSUID|MS_NOEXEC|MS_STRICTATIME,
{ "devtmpfs", "/dev", "devtmpfs", "mode=755" TMPFS_LIMITS_DEV, MS_NOSUID|MS_STRICTATIME,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "securityfs", "/sys/kernel/security", "securityfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_NONE },