Re: [PATCH] fscrypto: require write access to mount to set encryption policy

On Sat, Sep 10, 2016 at 12:15:19AM -0400, Theodore Ts'o wrote:

On Thu, Sep 08, 2016 at 02:20:38PM -0700, Eric Biggers wrote:

quoted

[To apply cleanly, my other two patches must be applied before this one]

Since setting an encryption policy requires writing metadata to the
filesystem, it should be guarded by mnt_want_write/mnt_drop_write.
Otherwise, a user could cause a write to a frozen or readonly
filesystem.  This was handled correctly by f2fs but not by ext4.  Make
fscrypt_process_policy() handle it rather than relying on the filesystem
to get it right.

Signed-off-by: Eric Biggers <redacted>

Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>

quoted

Cc: stable@vger.kernel.org # 4.1+; check fs/{ext4,f2fs}

Thanks, I have this in the ext4.git's fixes branch, but I plan to only
send the other two fixes to Linus, since (a) they are more critical,
and I'd prefer to get an Acked-by from Jaeguk or Changman (as the f2fs
maintainers) before I send this fix to Linus, since it touches f2fs.

Thank you, Ted.

It'd be better to fix the below basic warnings tho.

# ./scripts/checkpatch.pl [patch]

WARNING: line over 80 characters
#147: FILE: fs/crypto/policy.c:120:
+			ret = create_encryption_context_from_policy(inode, policy);

WARNING: line over 80 characters
#148: FILE: fs/crypto/policy.c:121:
+	} else if (!is_encryption_context_consistent_with_policy(inode, policy)) {

	WARNING: Prefer [subsystem eg: netdev]_warn([subsystem]dev, ... then dev_warn(dev, ... then pr_warn(...  to printk(KERN_WARNING ...
#149: FILE: fs/crypto/policy.c:122:
+		printk(KERN_WARNING

total: 0 errors, 3 warnings, 107 lines checked

Thanks,

							- Ted

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