Messages in this thread Patch in this message | | | Date | Wed, 8 May 2019 21:15:35 -0700 | From | Jaegeuk Kim <> | Subject | Re: [PATCH v5] f2fs: fix to avoid accessing xattr across the boundary |
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On 04/11, 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> > --- > v2: > * return EFAULT if OOB error is detected > > v3: > * fix typo in setxattr() > > v4: > * change boundry definition > > v5: > * revise boundry definition > --- > fs/f2fs/xattr.c | 32 +++++++++++++++++++++++++++----- > 1 file changed, 27 insertions(+), 5 deletions(-) > > diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c > index 848a785abe25..587429e29a69 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 +318,8 @@ 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;
I just found this should be + XATTR_PADDING_SIZE. Otherwise, generic/026 fails. Let me know, if there is any other concern below.
--- fs/f2fs/xattr.c | 12 ++++-------- fs/f2fs/xattr.h | 2 ++ 2 files changed, 6 insertions(+), 8 deletions(-)
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c index 019778fb9a0d..cd199a09d436 100644 --- a/fs/f2fs/xattr.c +++ b/fs/f2fs/xattr.c @@ -306,19 +306,18 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage, 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); int err = 0; - if (!size && !inline_size) + if (!xnid && !inline_size) return -ENODATA; - *base_size = inline_size + size + XATTR_PADDING_SIZE; + *base_size = XATTR_SIZE(xnid, inode); txattr_addr = f2fs_kzalloc(F2FS_I_SB(inode), *base_size, GFP_NOFS); if (!txattr_addr) return -ENOMEM; - last_txattr_addr = (void *)txattr_addr + inline_size + size; + last_txattr_addr = (void *)txattr_addr + *base_size; /* read from inline xattr */ if (inline_size) { @@ -599,9 +598,6 @@ static int __f2fs_setxattr(struct inode *inode, int index, size_t len; __u32 new_hsize; nid_t xnid = F2FS_I(inode)->i_xattr_nid; - unsigned int xnode_size = xnid ? VALID_XATTR_BLOCK_SIZE : 0; - unsigned int inline_size = inline_xattr_size(inode); - int error = 0; if (name == NULL) @@ -621,7 +617,7 @@ 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 + xnode_size + inline_size; + last_base_addr = (void *)base_addr + XATTR_SIZE(xnid, inode); /* find entry with wanted name. */ here = __find_xattr(base_addr, last_base_addr, index, len, name); diff --git a/fs/f2fs/xattr.h b/fs/f2fs/xattr.h index 9172ee082ca8..1eca1a2d996a 100644 --- a/fs/f2fs/xattr.h +++ b/fs/f2fs/xattr.h @@ -71,6 +71,8 @@ struct f2fs_xattr_entry { entry = XATTR_NEXT_ENTRY(entry)) #define VALID_XATTR_BLOCK_SIZE (PAGE_SIZE - sizeof(struct node_footer)) #define XATTR_PADDING_SIZE (sizeof(__u32)) +#define XATTR_SIZE(x,i) (((x) ? VALID_XATTR_BLOCK_SIZE : 0) + \ + (inline_xattr_size(i)) + XATTR_PADDING_SIZE) #define MIN_OFFSET(i) XATTR_ALIGN(inline_xattr_size(i) + \ VALID_XATTR_BLOCK_SIZE) -- 2.19.0.605.g01d371f741-goog
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