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ebiggerstytso
ebiggers
authored and
tytso
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fscrypt: pass up error codes from ->get_context()
It was possible for the ->get_context() operation to fail with a specific error code, which was then not returned to the caller of FS_IOC_SET_ENCRYPTION_POLICY or FS_IOC_GET_ENCRYPTION_POLICY. Make sure to pass through these error codes. Also reorganize the code so that ->get_context() only needs to be called one time when setting an encryption policy, and handle contexts of unrecognized sizes more appropriately. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Lines changed: 23 additions & 31 deletions

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‎fs/crypto/policy.c‎

Lines changed: 23 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -13,37 +13,20 @@
1313
#include <linux/mount.h>
1414
#include "fscrypt_private.h"
1515

16-
static int inode_has_encryption_context(struct inode *inode)
17-
{
18-
if (!inode->i_sb->s_cop->get_context)
19-
return 0;
20-
return (inode->i_sb->s_cop->get_context(inode, NULL, 0L) > 0);
21-
}
22-
2316
/*
24-
* check whether the policy is consistent with the encryption context
25-
* for the inode
17+
* check whether an encryption policy is consistent with an encryption context
2618
*/
27-
static int is_encryption_context_consistent_with_policy(struct inode *inode,
19+
static bool is_encryption_context_consistent_with_policy(
20+
const struct fscrypt_context *ctx,
2821
const struct fscrypt_policy *policy)
2922
{
30-
struct fscrypt_context ctx;
31-
int res;
32-
33-
if (!inode->i_sb->s_cop->get_context)
34-
return 0;
35-
36-
res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
37-
if (res != sizeof(ctx))
38-
return 0;
39-
40-
return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
41-
FS_KEY_DESCRIPTOR_SIZE) == 0 &&
42-
(ctx.flags == policy->flags) &&
43-
(ctx.contents_encryption_mode ==
44-
policy->contents_encryption_mode) &&
45-
(ctx.filenames_encryption_mode ==
46-
policy->filenames_encryption_mode));
23+
return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor,
24+
FS_KEY_DESCRIPTOR_SIZE) == 0 &&
25+
(ctx->flags == policy->flags) &&
26+
(ctx->contents_encryption_mode ==
27+
policy->contents_encryption_mode) &&
28+
(ctx->filenames_encryption_mode ==
29+
policy->filenames_encryption_mode);
4730
}
4831

4932
static int create_encryption_context_from_policy(struct inode *inode,
@@ -90,6 +73,7 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
9073
struct fscrypt_policy policy;
9174
struct inode *inode = file_inode(filp);
9275
int ret;
76+
struct fscrypt_context ctx;
9377

9478
if (copy_from_user(&policy, arg, sizeof(policy)))
9579
return -EFAULT;
@@ -106,7 +90,8 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
10690

10791
inode_lock(inode);
10892

109-
if (!inode_has_encryption_context(inode)) {
93+
ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
94+
if (ret == -ENODATA) {
11095
if (!S_ISDIR(inode->i_mode))
11196
ret = -ENOTDIR;
11297
else if (!inode->i_sb->s_cop->empty_dir)
@@ -116,8 +101,13 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
116101
else
117102
ret = create_encryption_context_from_policy(inode,
118103
&policy);
119-
} else if (!is_encryption_context_consistent_with_policy(inode,
120-
&policy)) {
104+
} else if (ret == sizeof(ctx) &&
105+
is_encryption_context_consistent_with_policy(&ctx,
106+
&policy)) {
107+
/* The file already uses the same encryption policy. */
108+
ret = 0;
109+
} else if (ret >= 0 || ret == -ERANGE) {
110+
/* The file already uses a different encryption policy. */
121111
ret = -EEXIST;
122112
}
123113

@@ -140,8 +130,10 @@ int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
140130
return -ENODATA;
141131

142132
res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
133+
if (res < 0 && res != -ERANGE)
134+
return res;
143135
if (res != sizeof(ctx))
144-
return -ENODATA;
136+
return -EINVAL;
145137
if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
146138
return -EINVAL;
147139

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