From c22f91d82cb9a29d22bdffdce6c803467984ad0c Mon Sep 17 00:00:00 2001 From: Weiming Shi Date: Wed, 24 Jun 2026 21:00:38 -0700 Subject: [PATCH] fs/ntfs3: validate ef->size covers the record's name and value When an EA record has a non-zero ef->size, ntfs_read_ea() only checks that the record fits in the remaining buffer (ea_size > bytes), not that ef->size is large enough to hold the record's own name_len + 1 + elength. A crafted image can pass validation with, e.g., ef->size = 24 but elength = 0xffff. ntfs_get_ea() then trusts elength and copies it out of the undersized record, reading past the kmalloc(info->size) allocation and leaking heap memory to userspace via getxattr(): BUG: KASAN: slab-out-of-bounds in ntfs_get_ea (fs/ntfs3/xattr.c:302) Read of size 65535 at addr ffff888100794550 by task exploit __asan_memcpy (mm/kasan/shadow.c:105) ntfs_get_ea (fs/ntfs3/xattr.c:302) ntfs_getxattr (fs/ntfs3/xattr.c:848) __vfs_getxattr (fs/xattr.c:441) vfs_getxattr (fs/xattr.c:474) do_getxattr (fs/xattr.c:800) path_getxattrat (fs/xattr.c:868) do_syscall_64 (arch/x86/entry/syscall_64.c:94) The buggy address is located 80 bytes inside of allocated 84-byte region in cache kmalloc-96 Compute the size the record needs and require ef->size to cover it. Fixes: 0e8235d28f3a ("fs/ntfs3: Check fields while reading") Reported-by: Xiang Mei Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Weiming Shi Signed-off-by: Konstantin Komarov --- fs/ntfs3/xattr.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/fs/ntfs3/xattr.c b/fs/ntfs3/xattr.c index 7a81369a1173..594ef6860b93 100644 --- a/fs/ntfs3/xattr.c +++ b/fs/ntfs3/xattr.c @@ -146,26 +146,29 @@ static int ntfs_read_ea(struct ntfs_inode *ni, struct EA_FULL **ea, for (off = 0; off < size; off += ea_size) { const struct EA_FULL *ef = Add2Ptr(ea_p, off); u32 bytes = size - off; + size_t need; /* Check if we can use field ea->size. */ if (bytes < sizeof(ef->size)) goto out1; - if (ef->size) { - ea_size = le32_to_cpu(ef->size); - if (ea_size > bytes) - goto out1; - continue; - } - /* Check if we can use fields ef->name_len and ef->elength. */ if (bytes < offsetof(struct EA_FULL, name)) goto out1; - ea_size = ALIGN(struct_size(ef, name, - 1 + ef->name_len + - le16_to_cpu(ef->elength)), - 4); + /* Size needed to hold this record's name and value. */ + need = struct_size(ef, name, + 1 + ef->name_len + le16_to_cpu(ef->elength)); + + if (ef->size) { + ea_size = le32_to_cpu(ef->size); + /* ef->size must fit the list and cover the record. */ + if (ea_size > bytes || ea_size < need) + goto out1; + continue; + } + + ea_size = ALIGN(need, 4); if (ea_size > bytes) goto out1; }