On 2019/4/10 17:27, Randall Huang wrote: > 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 [<ffffff900809003c>] dump_backtrace+0x0/0x6bc > [ 38.402966] c7 1827 [<ffffff9008090030>] show_stack+0x20/0x2c > [ 38.402981] c7 1827 [<ffffff900871ab10>] dump_stack+0xfc/0x140 > [ 38.402995] c7 1827 [<ffffff9008325c40>] > print_address_description+0x80/0x2d8 > [ 38.403009] c7 1827 [<ffffff900832629c>] kasan_report_error+0x198/0x1fc > [ 38.403022] c7 1827 [<ffffff9008326104>] kasan_report_error+0x0/0x1fc > [ 38.403037] c7 1827 [<ffffff9008325000>] __asan_load4+0x1b0/0x1b8 > [ 38.403051] c7 1827 [<ffffff90085fcc44>] f2fs_getxattr+0x518/0x68c > [ 38.403066] c7 1827 [<ffffff90085fc508>] f2fs_xattr_generic_get+0xb0/0xd0 > [ 38.403080] c7 1827 [<ffffff9008395708>] __vfs_getxattr+0x1f4/0x1fc > [ 38.403096] c7 1827 [<ffffff9008621bd0>] > inode_doinit_with_dentry+0x360/0x938 > [ 38.403109] c7 1827 [<ffffff900862d6cc>] selinux_d_instantiate+0x2c/0x38 > [ 38.403123] c7 1827 [<ffffff900861b018>] security_d_instantiate+0x68/0x98 > [ 38.403136] c7 1827 [<ffffff9008377db8>] d_splice_alias+0x58/0x348 > [ 38.403149] c7 1827 [<ffffff900858d16c>] f2fs_lookup+0x608/0x774 > [ 38.403163] c7 1827 [<ffffff900835eacc>] lookup_slow+0x1e0/0x2cc > [ 38.403177] c7 1827 [<ffffff9008367fe0>] walk_component+0x160/0x520 > [ 38.403190] c7 1827 [<ffffff9008369ef4>] path_lookupat+0x110/0x2b4 > [ 38.403203] c7 1827 [<ffffff900835dd38>] filename_lookup+0x1d8/0x3a8 > [ 38.403216] c7 1827 [<ffffff900835eeb0>] user_path_at_empty+0x54/0x68 > [ 38.403229] c7 1827 [<ffffff9008395f44>] SyS_getxattr+0xb4/0x18c > [ 38.403241] c7 1827 [<ffffff9008084200>] el0_svc_naked+0x34/0x38 > > Bug: 126558260 > > Signed-off-by: Randall Huang <[email protected]> > --- > v2: > * return EFAULT if OOB error is detected > > v3: > * fix typo in setxattr() > > v4: > * change boundry definition > --- > fs/f2fs/xattr.c | 34 +++++++++++++++++++++++++++++----- > 1 file changed, 29 insertions(+), 5 deletions(-) > > diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c > index 848a785abe25..a1cf53c727b2 100644 > --- a/fs/f2fs/xattr.c > +++ b/fs/f2fs/xattr.c > @@ -202,12 +202,18 @@ 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, > + void *last_base_addr, int index, > + size_t len, const char *name) > { > struct f2fs_xattr_entry *entry; > > list_for_each_xattr(entry, base_addr) { > + if ((void *)(entry) + sizeof(__u32) > last_base_addr || > + (void *)XATTR_NEXT_ENTRY(entry) + > + sizeof(__u32) > last_base_addr) > + return NULL; > + > if (entry->e_name_index != index) > continue; > if (entry->e_name_len != len) > @@ -298,6 +304,7 @@ static int lookup_all_xattrs(struct inode *inode, struct > page *ipage, > void **base_addr, int *base_size) > { > void *cur_addr, *txattr_addr, *last_addr = NULL; > + void *last_txattr_addr = NULL; > 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); > @@ -311,6 +318,9 @@ static int lookup_all_xattrs(struct inode *inode, struct > page *ipage, > if (!txattr_addr) > return -ENOMEM; > > + last_txattr_addr = (void *)txattr_addr + inline_size + size + > + XATTR_PADDING_SIZE - 1
The reserved 4 (XATTR_PADDING_SIZE) bytes space is not exist in on-disk layout, it only existS in memory space. We keep this reserved space for the condition that all space of xattr are valid, and in __find_xattr(), @entry will point to this space after entry = XATTR_NEXT_ENTRY(entry), and since the reserved space is always zeroed, then the loop can end up due to !IS_XATTR_LAST_ENTRY(entry) condition. So any entry touches or crosses the reserved space, that's illegal. You can check the layout in below commit. :) https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git/commit/?id=22588f8773f687449ce6e97dce9f102553440d30 So, how about this? last_txattr_addr = txattr_addr + inline_size + size; if ((void *)(entry) + sizeof(__u32) > last_base_addr || (void *)XATTR_NEXT_ENTRY(entry) > last_base_addr) return NULL; Thanks, > + > /* read from inline xattr */ > if (inline_size) { > err = read_inline_xattr(inode, ipage, txattr_addr); > @@ -337,7 +347,11 @@ 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, last_txattr_addr, index, len, name); > + if (!*xe) { > + err = -EFAULT; > + goto out; > + } > check: > if (IS_XATTR_LAST_ENTRY(*xe)) { > err = -ENODATA; > @@ -581,10 +595,15 @@ static int __f2fs_setxattr(struct inode *inode, int > index, > struct page *ipage, int flags) > { > struct f2fs_xattr_entry *here, *last; > - void *base_addr; > + void *base_addr, *last_base_addr = NULL; > 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 + xattr_nid_size + > + XATTR_PADDING_SIZE; > int error = 0; > > if (name == NULL) > @@ -604,9 +623,14 @@ static int __f2fs_setxattr(struct inode *inode, int > index, > error = read_all_xattrs(inode, ipage, &base_addr); > if (error) > return error; > + last_base_addr = (void *)base_addr + max_size - 1; > > /* find entry with wanted name. */ > - here = __find_xattr(base_addr, index, len, name); > + here = __find_xattr(base_addr, last_base_addr, index, len, name); > + if (!here) { > + error = -EFAULT; > + goto exit; > + } > > found = IS_XATTR_LAST_ENTRY(here) ? 0 : 1; > > _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
