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f2fs: sanity check of xattr entry size

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There is a security report where f2fs_getxattr() has a hole to expose wrong
memory region when the image is malformed like this.

f2fs_getxattr: entry->e_name_len: 4, size: 12288, buffer_size: 16384, len: 4

Cc: <stable@vger.kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Jaegeuk Kim 2018-12-26 19:54:07 -08:00
parent 60aa4d5536
commit 64beba0558
1 changed files with 13 additions and 5 deletions
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18
fs/f2fs/xattr.c
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@ -288,7 +288,7 @@ static int read_xattr_block(struct inode *inode, void *txattr_addr)
static int lookup_all_xattrs(struct inode *inode, struct page *ipage,
unsigned int index, unsigned int len,
const char *name, struct f2fs_xattr_entry **xe,
void **base_addr)
void **base_addr, int *base_size)
{
void *cur_addr, *txattr_addr, *last_addr = NULL;
nid_t xnid = F2FS_I(inode)->i_xattr_nid;
@ -299,8 +299,8 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage,
if (!size && !inline_size)
return -ENODATA;
txattr_addr = f2fs_kzalloc(F2FS_I_SB(inode),
inline_size + size + XATTR_PADDING_SIZE, GFP_NOFS);
*base_size = inline_size + size + XATTR_PADDING_SIZE;
txattr_addr = f2fs_kzalloc(F2FS_I_SB(inode), *base_size, GFP_NOFS);
if (!txattr_addr)
return -ENOMEM;
@ -312,8 +312,10 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage,
*xe = __find_inline_xattr(inode, txattr_addr, &last_addr,
index, len, name);
if (*xe)
if (*xe) {
*base_size = inline_size;
goto check;
}
}
/* read from xattr node block */
@ -474,6 +476,7 @@ int f2fs_getxattr(struct inode *inode, int index, const char *name,
int error = 0;
unsigned int size, len;
void *base_addr = NULL;
int base_size;
if (name == NULL)
return -EINVAL;
@ -484,7 +487,7 @@ int f2fs_getxattr(struct inode *inode, int index, const char *name,
down_read(&F2FS_I(inode)->i_xattr_sem);
error = lookup_all_xattrs(inode, ipage, index, len, name,
&entry, &base_addr);
&entry, &base_addr, &base_size);
up_read(&F2FS_I(inode)->i_xattr_sem);
if (error)
return error;
@ -498,6 +501,11 @@ int f2fs_getxattr(struct inode *inode, int index, const char *name,
if (buffer) {
char *pval = entry->e_name + entry->e_name_len;
if (base_size - (pval - (char *)base_addr) < size) {
error = -ERANGE;
goto out;
}
memcpy(buffer, pval, size);
}
error = size;