* [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
* 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
* [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 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
end of thread, other threads:[~2024-05-28 11:30 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 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 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 2024-05-17 10:53 ` Joseph Qi 2024-05-28 11:30 ` lei lu
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