From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Eric Biggers <ebiggers@google.com>
Subject: [PATCH 4.19 02/35] fscrypt: add fscrypt_is_nokey_name()
Date: Mon, 4 Jan 2021 16:57:05 +0100 [thread overview]
Message-ID: <20210104155703.499138033@linuxfoundation.org> (raw)
In-Reply-To: <20210104155703.375788488@linuxfoundation.org>
From: Eric Biggers <ebiggers@google.com>
commit 159e1de201b6fca10bfec50405a3b53a561096a8 upstream.
It's possible to create a duplicate filename in an encrypted directory
by creating a file concurrently with adding the encryption key.
Specifically, sys_open(O_CREAT) (or sys_mkdir(), sys_mknod(), or
sys_symlink()) can lookup the target filename while the directory's
encryption key hasn't been added yet, resulting in a negative no-key
dentry. The VFS then calls ->create() (or ->mkdir(), ->mknod(), or
->symlink()) because the dentry is negative. Normally, ->create() would
return -ENOKEY due to the directory's key being unavailable. However,
if the key was added between the dentry lookup and ->create(), then the
filesystem will go ahead and try to create the file.
If the target filename happens to already exist as a normal name (not a
no-key name), a duplicate filename may be added to the directory.
In order to fix this, we need to fix the filesystems to prevent
->create(), ->mkdir(), ->mknod(), and ->symlink() on no-key names.
(->rename() and ->link() need it too, but those are already handled
correctly by fscrypt_prepare_rename() and fscrypt_prepare_link().)
In preparation for this, add a helper function fscrypt_is_nokey_name()
that filesystems can use to do this check. Use this helper function for
the existing checks that fs/crypto/ does for rename and link.
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20201118075609.120337-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/crypto/hooks.c | 10 +++++-----
include/linux/fscrypt_notsupp.h | 5 +++++
include/linux/fscrypt_supp.h | 29 +++++++++++++++++++++++++++++
3 files changed, 39 insertions(+), 5 deletions(-)
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -58,8 +58,8 @@ int __fscrypt_prepare_link(struct inode
if (err)
return err;
- /* ... in case we looked up ciphertext name before key was added */
- if (dentry->d_flags & DCACHE_ENCRYPTED_NAME)
+ /* ... in case we looked up no-key name before key was added */
+ if (fscrypt_is_nokey_name(dentry))
return -ENOKEY;
if (!fscrypt_has_permitted_context(dir, inode))
@@ -83,9 +83,9 @@ int __fscrypt_prepare_rename(struct inod
if (err)
return err;
- /* ... in case we looked up ciphertext name(s) before key was added */
- if ((old_dentry->d_flags | new_dentry->d_flags) &
- DCACHE_ENCRYPTED_NAME)
+ /* ... in case we looked up no-key name(s) before key was added */
+ if (fscrypt_is_nokey_name(old_dentry) ||
+ fscrypt_is_nokey_name(new_dentry))
return -ENOKEY;
if (old_dir != new_dir) {
--- a/include/linux/fscrypt_notsupp.h
+++ b/include/linux/fscrypt_notsupp.h
@@ -24,6 +24,11 @@ static inline bool fscrypt_dummy_context
return false;
}
+static inline bool fscrypt_is_nokey_name(const struct dentry *dentry)
+{
+ return false;
+}
+
/* crypto.c */
static inline void fscrypt_enqueue_decrypt_work(struct work_struct *work)
{
--- a/include/linux/fscrypt_supp.h
+++ b/include/linux/fscrypt_supp.h
@@ -58,6 +58,35 @@ static inline bool fscrypt_dummy_context
inode->i_sb->s_cop->dummy_context(inode);
}
+/**
+ * fscrypt_is_nokey_name() - test whether a dentry is a no-key name
+ * @dentry: the dentry to check
+ *
+ * This returns true if the dentry is a no-key dentry. A no-key dentry is a
+ * dentry that was created in an encrypted directory that hasn't had its
+ * encryption key added yet. Such dentries may be either positive or negative.
+ *
+ * When a filesystem is asked to create a new filename in an encrypted directory
+ * and the new filename's dentry is a no-key dentry, it must fail the operation
+ * with ENOKEY. This includes ->create(), ->mkdir(), ->mknod(), ->symlink(),
+ * ->rename(), and ->link(). (However, ->rename() and ->link() are already
+ * handled by fscrypt_prepare_rename() and fscrypt_prepare_link().)
+ *
+ * This is necessary because creating a filename requires the directory's
+ * encryption key, but just checking for the key on the directory inode during
+ * the final filesystem operation doesn't guarantee that the key was available
+ * during the preceding dentry lookup. And the key must have already been
+ * available during the dentry lookup in order for it to have been checked
+ * whether the filename already exists in the directory and for the new file's
+ * dentry not to be invalidated due to it incorrectly having the no-key flag.
+ *
+ * Return: %true if the dentry is a no-key name
+ */
+static inline bool fscrypt_is_nokey_name(const struct dentry *dentry)
+{
+ return dentry->d_flags & DCACHE_ENCRYPTED_NAME;
+}
+
/* crypto.c */
extern void fscrypt_enqueue_decrypt_work(struct work_struct *);
extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);
next prev parent reply other threads:[~2021-01-04 16:14 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-04 15:57 [PATCH 4.19 00/35] 4.19.165-rc1 review Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 01/35] md/raid10: initialize r10_bio->read_slot before use Greg Kroah-Hartman
2021-01-04 15:57 ` Greg Kroah-Hartman [this message]
2021-01-04 15:57 ` [PATCH 4.19 03/35] ext4: prevent creating duplicate encrypted filenames Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 04/35] f2fs: " Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 05/35] ubifs: " Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 06/35] vfio/pci: Move dummy_resources_list init in vfio_pci_probe() Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 07/35] ext4: dont remount read-only with errors=continue on reboot Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 08/35] uapi: move constants from <linux/kernel.h> to <linux/const.h> Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 09/35] KVM: SVM: relax conditions for allowing MSR_IA32_SPEC_CTRL accesses Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 10/35] KVM: x86: reinstate vendor-agnostic check on SPEC_CTRL cpuid bits Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 11/35] powerpc/bitops: Fix possible undefined behaviour with fls() and fls64() Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 12/35] xen/gntdev.c: Mark pages as dirty Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 13/35] null_blk: Fix zone size initialization Greg Kroah-Hartman
2021-01-06 12:54 ` Pavel Machek
2021-01-11 2:46 ` Damien Le Moal
2021-01-04 15:57 ` [PATCH 4.19 14/35] of: fix linker-section match-table corruption Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 15/35] asm-generic/tlb: Track freeing of page-table directories in struct mmu_gather Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 16/35] asm-generic/tlb: Track which levels of the page tables have been cleared Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 17/35] asm-generic/tlb, arch: Invert CONFIG_HAVE_RCU_TABLE_INVALIDATE Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 18/35] powerpc/mmu_gather: enable RCU_TABLE_FREE even for !SMP case Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 19/35] mm/mmu_gather: invalidate TLB correctly on batch allocation failure and flush Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 20/35] asm-generic/tlb: avoid potential double flush Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 21/35] Bluetooth: hci_h5: close serdev device and free hu in h5_close Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 22/35] reiserfs: add check for an invalid ih_entry_count Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 23/35] misc: vmw_vmci: fix kernel info-leak by initializing dbells in vmci_ctx_get_chkpt_doorbells() Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 24/35] media: gp8psk: initialize stats at power control logic Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 25/35] ALSA: seq: Use bool for snd_seq_queue internal flags Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 26/35] ALSA: rawmidi: Access runtime->avail always in spinlock Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 27/35] fcntl: Fix potential deadlock in send_sig{io, urg}() Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 28/35] rtc: sun6i: Fix memleak in sun6i_rtc_clk_init Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 29/35] module: set MODULE_STATE_GOING state when a module fails to load Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 30/35] quota: Dont overflow quota file offsets Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 31/35] powerpc: sysdev: add missing iounmap() on error in mpic_msgr_probe() Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 32/35] NFSv4: Fix a pNFS layout related use-after-free race when freeing the inode Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 33/35] module: delay kobject uevent until after module init call Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 34/35] ALSA: pcm: Clear the full allocated memory at hw_params Greg Kroah-Hartman
2021-01-04 15:57 ` [PATCH 4.19 35/35] dm verity: skip verity work if I/O error when system is shutting down Greg Kroah-Hartman
2021-01-04 17:43 ` [PATCH 4.19 00/35] 4.19.165-rc1 review Daniel Díaz
2021-01-05 9:06 ` Greg Kroah-Hartman
2021-01-04 19:59 ` Pavel Machek
2021-01-04 21:09 ` Jon Hunter
2021-01-05 1:58 ` Guenter Roeck
2021-01-05 9:06 ` Greg Kroah-Hartman
2021-01-05 16:44 ` Shuah Khan
2021-01-06 13:46 ` Greg Kroah-Hartman
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