* [PATCH v2 0/2] ocfs2: add checks in ocfs2_xattr_find_entry() to avoid potential out-of-bound access.
@ 2024-05-17 9:41 Ferry Meng
2024-05-17 9:41 ` [PATCH v2 1/2] ocfs2: add bounds checking to ocfs2_xattr_find_entry() Ferry Meng
2024-05-17 9:41 ` [PATCH v2 2/2] ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry() Ferry Meng
0 siblings, 2 replies; 6+ messages in thread
From: Ferry Meng @ 2024-05-17 9:41 UTC (permalink / raw)
To: Mark Fasheh, Joel Becker, Joseph Qi, ocfs2-devel; +Cc: linux-kernel, Ferry Meng
Hi, all:
This patch series attempts to address a scenario where accessing user-defined
xattrs in a carefully crafted image can lead to out-of-bound access.(To speak
truthfully, I do not think this vehavior would occur under proper usage.)
In my testing environment, I constructed an OCFS2 image, created a file with
several user-defined xattrs(long name attributes, this will cause a "Non-INLINE"
xattr, which requires additional space for storage), and then forcibly modified
the xe_name_offset using a binary editing tool (e.g "hexedit"). Upon remounting
the image and running 'getfattr -d /path/to/file', this patchset was able to
detect "partial" malicious modification.
In v2, I make these changes:
- (1/2) use xs->end directly, no need to parse a parameter.
- (2/2) define a local var 'name_offset'.
Ferry Meng (2):
ocfs2: add bounds checking to ocfs2_xattr_find_entry()
ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry()
fs/ocfs2/xattr.c | 27 ++++++++++++++++++---------
1 file changed, 18 insertions(+), 9 deletions(-)
--
2.32.0.3.g01195cf9f
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2 1/2] ocfs2: add bounds checking to ocfs2_xattr_find_entry()
2024-05-17 9:41 [PATCH v2 0/2] ocfs2: add checks in ocfs2_xattr_find_entry() to avoid potential out-of-bound access Ferry Meng
@ 2024-05-17 9:41 ` Ferry Meng
2024-05-17 10:52 ` Joseph Qi
2024-05-17 9:41 ` [PATCH v2 2/2] ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry() Ferry Meng
1 sibling, 1 reply; 6+ messages in thread
From: Ferry Meng @ 2024-05-17 9:41 UTC (permalink / raw)
To: Mark Fasheh, Joel Becker, Joseph Qi, ocfs2-devel; +Cc: linux-kernel, Ferry Meng
Add a paranoia check to make sure it doesn't stray beyond valid memory
region containing ocfs2 xattr entries when scanning for a match.
It will prevent out-of-bound access in case of crafted images.
Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
---
fs/ocfs2/xattr.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 3b81213ed7b8..8aea94c90739 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -1062,7 +1062,7 @@ ssize_t ocfs2_listxattr(struct dentry *dentry,
return i_ret + b_ret;
}
-static int ocfs2_xattr_find_entry(int name_index,
+static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
const char *name,
struct ocfs2_xattr_search *xs)
{
@@ -1076,6 +1076,10 @@ static int ocfs2_xattr_find_entry(int name_index,
name_len = strlen(name);
entry = xs->here;
for (i = 0; i < le16_to_cpu(xs->header->xh_count); i++) {
+ if ((void *)entry >= xs->end) {
+ ocfs2_error(inode->i_sb, "corrupted xattr entries");
+ return -EFSCORRUPTED;
+ }
cmp = name_index - ocfs2_xattr_get_type(entry);
if (!cmp)
cmp = name_len - entry->xe_name_len;
@@ -1166,7 +1170,7 @@ static int ocfs2_xattr_ibody_get(struct inode *inode,
xs->base = (void *)xs->header;
xs->here = xs->header->xh_entries;
- ret = ocfs2_xattr_find_entry(name_index, name, xs);
+ ret = ocfs2_xattr_find_entry(inode, name_index, name, xs);
if (ret)
return ret;
size = le64_to_cpu(xs->here->xe_value_size);
@@ -2698,7 +2702,7 @@ static int ocfs2_xattr_ibody_find(struct inode *inode,
/* Find the named attribute. */
if (oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL) {
- ret = ocfs2_xattr_find_entry(name_index, name, xs);
+ ret = ocfs2_xattr_find_entry(inode, name_index, name, xs);
if (ret && ret != -ENODATA)
return ret;
xs->not_found = ret;
@@ -2833,7 +2837,7 @@ static int ocfs2_xattr_block_find(struct inode *inode,
xs->end = (void *)(blk_bh->b_data) + blk_bh->b_size;
xs->here = xs->header->xh_entries;
- ret = ocfs2_xattr_find_entry(name_index, name, xs);
+ ret = ocfs2_xattr_find_entry(inode, name_index, name, xs);
} else
ret = ocfs2_xattr_index_block_find(inode, blk_bh,
name_index,
--
2.32.0.3.g01195cf9f
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v2 2/2] ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry()
2024-05-17 9:41 [PATCH v2 0/2] ocfs2: add checks in ocfs2_xattr_find_entry() to avoid potential out-of-bound access Ferry Meng
2024-05-17 9:41 ` [PATCH v2 1/2] ocfs2: add bounds checking to ocfs2_xattr_find_entry() Ferry Meng
@ 2024-05-17 9:41 ` Ferry Meng
2024-05-17 10:53 ` Joseph Qi
1 sibling, 1 reply; 6+ messages in thread
From: Ferry Meng @ 2024-05-17 9:41 UTC (permalink / raw)
To: Mark Fasheh, Joel Becker, Joseph Qi, ocfs2-devel; +Cc: linux-kernel, Ferry Meng
xattr in ocfs2 maybe 'non-indexed', which saved with additional space
requested. It's better to check if the memory is out of bound before
memcmp, although this possibility mainly comes from crafted poisonous
images.
Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
---
fs/ocfs2/xattr.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 8aea94c90739..35c0cc2a51af 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -1068,7 +1068,7 @@ static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
{
struct ocfs2_xattr_entry *entry;
size_t name_len;
- int i, cmp = 1;
+ int i, name_offset, cmp = 1;
if (name == NULL)
return -EINVAL;
@@ -1083,10 +1083,15 @@ static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
cmp = name_index - ocfs2_xattr_get_type(entry);
if (!cmp)
cmp = name_len - entry->xe_name_len;
- if (!cmp)
- cmp = memcmp(name, (xs->base +
- le16_to_cpu(entry->xe_name_offset)),
- name_len);
+ if (!cmp) {
+ name_offset = le16_to_cpu(entry->xe_name_offset);
+ if ((xs->base + name_offset + name_len) > xs->end) {
+ ocfs2_error(inode->i_sb,
+ "corrupted xattr entries");
+ return -EFSCORRUPTED;
+ }
+ cmp = memcmp(name, (xs->base + name_offset), name_len);
+ }
if (cmp == 0)
break;
entry += 1;
--
2.32.0.3.g01195cf9f
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2 1/2] ocfs2: add bounds checking to ocfs2_xattr_find_entry()
2024-05-17 9:41 ` [PATCH v2 1/2] ocfs2: add bounds checking to ocfs2_xattr_find_entry() Ferry Meng
@ 2024-05-17 10:52 ` Joseph Qi
0 siblings, 0 replies; 6+ messages in thread
From: Joseph Qi @ 2024-05-17 10:52 UTC (permalink / raw)
To: Ferry Meng, lei lu, akpm
Cc: linux-kernel, Mark Fasheh, Joel Becker, ocfs2-devel
On 5/17/24 5:41 PM, Ferry Meng wrote:
> Add a paranoia check to make sure it doesn't stray beyond valid memory
> region containing ocfs2 xattr entries when scanning for a match.
> It will prevent out-of-bound access in case of crafted images.
>
> Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
Reported-by: lei lu <llfamsec@gmail.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> ---
> fs/ocfs2/xattr.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index 3b81213ed7b8..8aea94c90739 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -1062,7 +1062,7 @@ ssize_t ocfs2_listxattr(struct dentry *dentry,
> return i_ret + b_ret;
> }
>
> -static int ocfs2_xattr_find_entry(int name_index,
> +static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
> const char *name,
> struct ocfs2_xattr_search *xs)
> {
> @@ -1076,6 +1076,10 @@ static int ocfs2_xattr_find_entry(int name_index,
> name_len = strlen(name);
> entry = xs->here;
> for (i = 0; i < le16_to_cpu(xs->header->xh_count); i++) {
> + if ((void *)entry >= xs->end) {
> + ocfs2_error(inode->i_sb, "corrupted xattr entries");
> + return -EFSCORRUPTED;
> + }
> cmp = name_index - ocfs2_xattr_get_type(entry);
> if (!cmp)
> cmp = name_len - entry->xe_name_len;
> @@ -1166,7 +1170,7 @@ static int ocfs2_xattr_ibody_get(struct inode *inode,
> xs->base = (void *)xs->header;
> xs->here = xs->header->xh_entries;
>
> - ret = ocfs2_xattr_find_entry(name_index, name, xs);
> + ret = ocfs2_xattr_find_entry(inode, name_index, name, xs);
> if (ret)
> return ret;
> size = le64_to_cpu(xs->here->xe_value_size);
> @@ -2698,7 +2702,7 @@ static int ocfs2_xattr_ibody_find(struct inode *inode,
>
> /* Find the named attribute. */
> if (oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL) {
> - ret = ocfs2_xattr_find_entry(name_index, name, xs);
> + ret = ocfs2_xattr_find_entry(inode, name_index, name, xs);
> if (ret && ret != -ENODATA)
> return ret;
> xs->not_found = ret;
> @@ -2833,7 +2837,7 @@ static int ocfs2_xattr_block_find(struct inode *inode,
> xs->end = (void *)(blk_bh->b_data) + blk_bh->b_size;
> xs->here = xs->header->xh_entries;
>
> - ret = ocfs2_xattr_find_entry(name_index, name, xs);
> + ret = ocfs2_xattr_find_entry(inode, name_index, name, xs);
> } else
> ret = ocfs2_xattr_index_block_find(inode, blk_bh,
> name_index,
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 2/2] ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry()
2024-05-17 9:41 ` [PATCH v2 2/2] ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry() Ferry Meng
@ 2024-05-17 10:53 ` Joseph Qi
2024-05-28 11:30 ` lei lu
0 siblings, 1 reply; 6+ messages in thread
From: Joseph Qi @ 2024-05-17 10:53 UTC (permalink / raw)
To: Ferry Meng, lei lu, akpm
Cc: linux-kernel, Mark Fasheh, Joel Becker, ocfs2-devel
On 5/17/24 5:41 PM, Ferry Meng wrote:
> xattr in ocfs2 maybe 'non-indexed', which saved with additional space
> requested. It's better to check if the memory is out of bound before
> memcmp, although this possibility mainly comes from crafted poisonous
> images.
>
> Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
Reported-by: lei lu <llfamsec@gmail.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> ---
> fs/ocfs2/xattr.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index 8aea94c90739..35c0cc2a51af 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -1068,7 +1068,7 @@ static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
> {
> struct ocfs2_xattr_entry *entry;
> size_t name_len;
> - int i, cmp = 1;
> + int i, name_offset, cmp = 1;
>
> if (name == NULL)
> return -EINVAL;
> @@ -1083,10 +1083,15 @@ static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
> cmp = name_index - ocfs2_xattr_get_type(entry);
> if (!cmp)
> cmp = name_len - entry->xe_name_len;
> - if (!cmp)
> - cmp = memcmp(name, (xs->base +
> - le16_to_cpu(entry->xe_name_offset)),
> - name_len);
> + if (!cmp) {
> + name_offset = le16_to_cpu(entry->xe_name_offset);
> + if ((xs->base + name_offset + name_len) > xs->end) {
> + ocfs2_error(inode->i_sb,
> + "corrupted xattr entries");
> + return -EFSCORRUPTED;
> + }
> + cmp = memcmp(name, (xs->base + name_offset), name_len);
> + }
> if (cmp == 0)
> break;
> entry += 1;
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 2/2] ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry()
2024-05-17 10:53 ` Joseph Qi
@ 2024-05-28 11:30 ` lei lu
0 siblings, 0 replies; 6+ messages in thread
From: lei lu @ 2024-05-28 11:30 UTC (permalink / raw)
To: joseph.qi
Cc: akpm, jlbec, linux-kernel, llfamsec, mark, mengferry, ocfs2-devel
Hi,
Maybe we should add the same check for ocfs2_xattr_list_entries.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2024-05-17 9:41 [PATCH v2 0/2] ocfs2: add checks in ocfs2_xattr_find_entry() to avoid potential out-of-bound access Ferry Meng
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