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authorTheodore Ts'o <tytso@mit.edu>2018-03-31 03:04:11 +0300
committerTheodore Ts'o <tytso@mit.edu>2018-03-31 03:04:11 +0300
commit54dd0e0a1b255f115f8647fc6fb93273251b01b9 (patch)
tree36f9de7bca64d5ec2459c6d3d9255fea76ea40fa /fs/ext4
parent9496005d6ca4cf8f5ee8f828165a8956872dc59d (diff)
downloadlinux-54dd0e0a1b255f115f8647fc6fb93273251b01b9.tar.xz
ext4: add extra checks to ext4_xattr_block_get()
Add explicit checks in ext4_xattr_block_get() just in case the e_value_offs and e_value_size fields in the the xattr block are corrupted in memory after the buffer_verified bit is set on the xattr block. Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@kernel.org
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/xattr.c26
-rw-r--r--fs/ext4/xattr.h11
2 files changed, 30 insertions, 7 deletions
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 6304e81bfe6a..499cb4b1fbd2 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -197,7 +197,7 @@ ext4_xattr_check_entries(struct ext4_xattr_entry *entry, void *end,
while (!IS_LAST_ENTRY(entry)) {
u32 size = le32_to_cpu(entry->e_value_size);
- if (size > INT_MAX)
+ if (size > EXT4_XATTR_SIZE_MAX)
return -EFSCORRUPTED;
if (size != 0 && entry->e_value_inum == 0) {
@@ -540,8 +540,10 @@ ext4_xattr_block_get(struct inode *inode, int name_index, const char *name,
if (error)
goto cleanup;
size = le32_to_cpu(entry->e_value_size);
+ error = -ERANGE;
+ if (unlikely(size > EXT4_XATTR_SIZE_MAX))
+ goto cleanup;
if (buffer) {
- error = -ERANGE;
if (size > buffer_size)
goto cleanup;
if (entry->e_value_inum) {
@@ -550,8 +552,12 @@ ext4_xattr_block_get(struct inode *inode, int name_index, const char *name,
if (error)
goto cleanup;
} else {
- memcpy(buffer, bh->b_data +
- le16_to_cpu(entry->e_value_offs), size);
+ u16 offset = le16_to_cpu(entry->e_value_offs);
+ void *p = bh->b_data + offset;
+
+ if (unlikely(p + size > end))
+ goto cleanup;
+ memcpy(buffer, p, size);
}
}
error = size;
@@ -589,8 +595,10 @@ ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
if (error)
goto cleanup;
size = le32_to_cpu(entry->e_value_size);
+ error = -ERANGE;
+ if (unlikely(size > EXT4_XATTR_SIZE_MAX))
+ goto cleanup;
if (buffer) {
- error = -ERANGE;
if (size > buffer_size)
goto cleanup;
if (entry->e_value_inum) {
@@ -599,8 +607,12 @@ ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
if (error)
goto cleanup;
} else {
- memcpy(buffer, (void *)IFIRST(header) +
- le16_to_cpu(entry->e_value_offs), size);
+ u16 offset = le16_to_cpu(entry->e_value_offs);
+ void *p = (void *)IFIRST(header) + offset;
+
+ if (unlikely(p + size > end))
+ goto cleanup;
+ memcpy(buffer, p, size);
}
}
error = size;
diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
index dd54c4f995c8..f39cad2abe2a 100644
--- a/fs/ext4/xattr.h
+++ b/fs/ext4/xattr.h
@@ -71,6 +71,17 @@ struct ext4_xattr_entry {
#define IFIRST(hdr) ((struct ext4_xattr_entry *)((hdr)+1))
/*
+ * XATTR_SIZE_MAX is currently 64k, but for the purposes of checking
+ * for file system consistency errors, we use a somewhat bigger value.
+ * This allows XATTR_SIZE_MAX to grow in the future, but by using this
+ * instead of INT_MAX for certain consistency checks, we don't need to
+ * worry about arithmetic overflows. (Actually XATTR_SIZE_MAX is
+ * defined in include/uapi/linux/limits.h, so changing it is going
+ * not going to be trivial....)
+ */
+#define EXT4_XATTR_SIZE_MAX (1 << 24)
+
+/*
* The minimum size of EA value when you start storing it in an external inode
* size of block - size of header - size of 1 entry - 4 null bytes
*/