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ext4: verify the depth of extent tree in ext4_find_extent()

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If there is a corupted file system where the claimed depth of the
extent tree is -1, this can cause a massive buffer overrun leading to
sadness.

This addresses CVE-2018-10877.

https://bugzilla.kernel.org/show_bug.cgi?id=199417

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
This commit is contained in:
Theodore Ts'o 2018-06-14 12:55:10 -04:00
parent 8844618d8a
commit bc890a6024
2 changed files with 7 additions and 0 deletions
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1
fs/ext4/ext4_extents.h
View file

@ -91,6 +91,7 @@ struct ext4_extent_header {
};
#define EXT4_EXT_MAGIC cpu_to_le16(0xf30a)
#define EXT4_MAX_EXTENT_DEPTH 5
#define EXT4_EXTENT_TAIL_OFFSET(hdr) \
(sizeof(struct ext4_extent_header) + \

6
fs/ext4/extents.c
View file

@ -869,6 +869,12 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block,
eh = ext_inode_hdr(inode);
depth = ext_depth(inode);
if (depth < 0 || depth > EXT4_MAX_EXTENT_DEPTH) {
EXT4_ERROR_INODE(inode, "inode has invalid extent depth: %d",
depth);
ret = -EFSCORRUPTED;
goto err;
}
if (path) {
ext4_ext_drop_refs(path);