Messages in this thread | | | Subject | Re: [f2fs-dev] [PATCH] f2fs: fix to avoid accessing xattr across the boundary | From | Chao Yu <> | Date | Mon, 8 Apr 2019 20:14:43 +0800 |
| |
On 2019/4/8 20:03, Chao Yu wrote: > Hi Randall, > > On 2019/4/8 16:50, 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 <huangrandall@google.com> >> --- >> fs/f2fs/xattr.c | 22 ++++++++++++++++------ >> 1 file changed, 16 insertions(+), 6 deletions(-) >> >> diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c >> index 848a785abe25..0531c1e38275 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, >> + int base_addr_limit, int index, > > unsigned int max_size, > >> + size_t len, const char *name) >> { >> struct f2fs_xattr_entry *entry; >> + void *max_addr = base_addr + ENTRY_SIZE(XATTR_ENTRY(base_addr)) + >> + base_addr_limit - 1; > > If I'm not missing something, shouldn't it be? > > void *max_addr = base_addr + max_size; > >> >> 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) >> @@ -337,9 +342,9 @@ 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, XATTR_PADDING_SIZE, index, len, name); > > max_size = *base_size - (txattr_addr - cur_addr);
max_size = *base_size - (cur_addr - txattr_addr);
> *xe = __find_xattr(cur_addr, max_size, index, len, name); > >> check: >> - if (IS_XATTR_LAST_ENTRY(*xe)) { >> + if (!*xe || IS_XATTR_LAST_ENTRY(*xe)) { > > If xattr entry across boundary of max xattr space size, maybe we'd better return -EFAULT > which can be distinguished from a real -ENODATA error, latter, we can set SBI_NEED_FSCK > to give a repairing hint to fsck. :) > >> err = -ENODATA; >> goto out; >> } >> @@ -606,9 +611,14 @@ 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, inline_xattr_size(inode) + >> + VALID_XATTR_BLOCK_SIZE + XATTR_PADDING_SIZE, >> + index, len, name); > > unsigned int size = F2FS_I(inode)->i_xattr_nid ? VALID_XATTR_BLOCK_SIZE : 0; > unsigned int max_size = inline_xattr_size(inode) + size + XATTR_PADDING_SIZE; > > here = __find_xattr(..., max_size, ...); > > if (!here) > return -EFAULT; > > Thanks, > >> >> - found = IS_XATTR_LAST_ENTRY(here) ? 0 : 1; >> + if (!here) >> + found = 0; >> + else >> + found = IS_XATTR_LAST_ENTRY(here) ? 0 : 1; >> >> if (found) { >> if ((flags & XATTR_CREATE)) { >> > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > . >
| |