From mboxrd@z Thu Jan 1 00:00:00 1970 From: Randall Huang Subject: [PATCH v2] f2fs: fix to avoid accessing xattr across the boundary Date: Tue, 9 Apr 2019 16:37:26 +0800 Message-ID: <20190409083726.181522-1-huangrandall@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: Sender: linux-kernel-owner@vger.kernel.org To: jaegeuk@kernel.org, yuchao0@huawei.com, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Cc: huangrandall@google.com List-Id: linux-f2fs-devel.lists.sourceforge.net When we traverse xattr entries via __find_xattr(), if the raw filesystem content is faked or any hardware failure occurs, out-of-bound error can be detected by KASAN. Fix the issue by introducing boundary check. [ 38.402878] c7 1827 BUG: KASAN: slab-out-of-bounds in f2fs_getxattr+0x518/0x68c [ 38.402891] c7 1827 Read of size 4 at addr ffffffc0b6fb35dc by task [ 38.402935] c7 1827 Call trace: [ 38.402952] c7 1827 [] dump_backtrace+0x0/0x6bc [ 38.402966] c7 1827 [] show_stack+0x20/0x2c [ 38.402981] c7 1827 [] dump_stack+0xfc/0x140 [ 38.402995] c7 1827 [] print_address_description+0x80/0x2d8 [ 38.403009] c7 1827 [] kasan_report_error+0x198/0x1fc [ 38.403022] c7 1827 [] kasan_report_error+0x0/0x1fc [ 38.403037] c7 1827 [] __asan_load4+0x1b0/0x1b8 [ 38.403051] c7 1827 [] f2fs_getxattr+0x518/0x68c [ 38.403066] c7 1827 [] f2fs_xattr_generic_get+0xb0/0xd0 [ 38.403080] c7 1827 [] __vfs_getxattr+0x1f4/0x1fc [ 38.403096] c7 1827 [] inode_doinit_with_dentry+0x360/0x938 [ 38.403109] c7 1827 [] selinux_d_instantiate+0x2c/0x38 [ 38.403123] c7 1827 [] security_d_instantiate+0x68/0x98 [ 38.403136] c7 1827 [] d_splice_alias+0x58/0x348 [ 38.403149] c7 1827 [] f2fs_lookup+0x608/0x774 [ 38.403163] c7 1827 [] lookup_slow+0x1e0/0x2cc [ 38.403177] c7 1827 [] walk_component+0x160/0x520 [ 38.403190] c7 1827 [] path_lookupat+0x110/0x2b4 [ 38.403203] c7 1827 [] filename_lookup+0x1d8/0x3a8 [ 38.403216] c7 1827 [] user_path_at_empty+0x54/0x68 [ 38.403229] c7 1827 [] SyS_getxattr+0xb4/0x18c [ 38.403241] c7 1827 [] el0_svc_naked+0x34/0x38 Bug: 126558260 Signed-off-by: Randall Huang --- v2: * return EFAULT if OOB error is detected --- fs/f2fs/xattr.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c index 848a785abe25..f60e40d95bbf 100644 --- a/fs/f2fs/xattr.c +++ b/fs/f2fs/xattr.c @@ -202,12 +202,17 @@ static inline const struct xattr_handler *f2fs_xattr_handler(int index) return handler; } -static struct f2fs_xattr_entry *__find_xattr(void *base_addr, int index, - size_t len, const char *name) +static struct f2fs_xattr_entry *__find_xattr(void *base_addr, + unsigned int max_size, int index, + size_t len, const char *name) { struct f2fs_xattr_entry *entry; + void *max_addr = base_addr + ENTRY_SIZE(XATTR_ENTRY(base_addr)) + + max_size - 1; list_for_each_xattr(entry, base_addr) { + if ((void *)entry + sizeof(__u32) > max_addr) + return NULL; if (entry->e_name_index != index) continue; if (entry->e_name_len != len) @@ -301,6 +306,7 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage, nid_t xnid = F2FS_I(inode)->i_xattr_nid; unsigned int size = xnid ? VALID_XATTR_BLOCK_SIZE : 0; unsigned int inline_size = inline_xattr_size(inode); + unsigned int max_size = inline_size + size + XATTR_PADDING_SIZE; int err = 0; if (!size && !inline_size) @@ -323,6 +329,7 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage, *base_size = inline_size; goto check; } + max_size -= inline_size; } /* read from xattr node block */ @@ -330,6 +337,8 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage, err = read_xattr_block(inode, txattr_addr); if (err) goto out; + + max_size -= size; } if (last_addr) @@ -337,7 +346,12 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage, else cur_addr = txattr_addr; - *xe = __find_xattr(cur_addr, index, len, name); + *xe = __find_xattr(cur_addr, max_size, index, len, name); + if (!*xe) { + err = -EFAULT; + goto out; + } + check: if (IS_XATTR_LAST_ENTRY(*xe)) { err = -ENODATA; @@ -585,6 +599,10 @@ static int __f2fs_setxattr(struct inode *inode, int index, int found, newsize; size_t len; __u32 new_hsize; + nid_t xnid = F2FS_I(inode)->i_xattr_nid; + unsigned int xattr_nid_size = xnid ? VALID_XATTR_BLOCK_SIZE : 0; + unsigned int inline_size = inline_xattr_size(inode); + unsigned int max_size = inline_size + size + XATTR_PADDING_SIZE; int error = 0; if (name == NULL) @@ -606,7 +624,11 @@ static int __f2fs_setxattr(struct inode *inode, int index, return error; /* find entry with wanted name. */ - here = __find_xattr(base_addr, index, len, name); + here = __find_xattr(base_addr, max_size, index, len, name); + if (!here) { + error = -EFAULT; + goto exit; + } found = IS_XATTR_LAST_ENTRY(here) ? 0 : 1; -- 2.21.0.392.gf8f6787159e-goog