Messages in this thread Patch in this message | | | Subject | Re: [PATCH v5] f2fs: fix to avoid accessing xattr across the boundary | From | Chao Yu <> | Date | Thu, 9 May 2019 15:07:18 +0800 |
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On 2019/5/9 12:15, Jaegeuk Kim wrote: > 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.
We're trying to use [txattr_addr, last_txattr_addr] to indicate valid range of xattr datas, any valid entries across the boundary is not allowed, so I think it's correct to exclude padding space for last_txattr_addr.
I added log and tested generic/026, found that:
[365804.868431] base:ffff89e391f8e000, last:ffff89e391f8f0b0 [365804.868433] entry:ffff89e391f8e018, next:ffff89e391f8f0b0
The root cause of this issue is caused by below condition:
(void *)XATTR_NEXT_ENTRY(entry) + sizeof(__u32) > last_base_addr)
It occurs when the end address of last valid entry is located in range (last_base_addr - XATTR_PADDING_SIZE, last_base_addr], then next invalid entry's head will across last_base_addr, result in returning -EFAULT.
So anyway, please try below diff instead. ;)
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c index 019778fb9a0d..217bf7c2bb7a 100644 --- a/fs/f2fs/xattr.c +++ b/fs/f2fs/xattr.c @@ -210,10 +210,8 @@ static struct f2fs_xattr_entry *__find_xattr(void *base_addr,
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) + (void *)XATTR_NEXT_ENTRY(entry) > last_base_addr) return NULL;
if (entry->e_name_index != index)
Thanks,
> --- > 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) > >
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