From: Eric Biggers <ebiggers@xxxxxxxxxx> This is a replacement for the broken patch "ext4: add better range checking for e_value_size in xattrs" currently in ext4/dev. -----8<----- ext4 isn't validating the sizes of xattrs that are stored in external inodes. This is problematic because ->e_value_size is a u32, but ext4_xattr_get() returns an int. A very large size is misinterpreted as an error code, which ext4_get_acl() translates into a bogus ERR_PTR() for which IS_ERR() returns false, causing a crash. Fix this by validating that all xattrs are <= XATTR_SIZE_MAX bytes. (It's not strictly needed for non-EA-inode xattrs, but it doesn't hurt.) https://bugzilla.kernel.org/show_bug.cgi?id=199185 Reported-by: Wen Xu <wen.xu@xxxxxxxxxx> Fixes: e50e5129f384 ("ext4: xattr-in-inode support") Cc: <stable@xxxxxxxxxxxxxxx> # v4.13+ Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> --- fs/ext4/xattr.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index 63656dbafdc45..8c9ade64aea2a 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -195,10 +195,13 @@ ext4_xattr_check_entries(struct ext4_xattr_entry *entry, void *end, /* Check the values */ while (!IS_LAST_ENTRY(entry)) { - if (entry->e_value_size != 0 && - entry->e_value_inum == 0) { + u32 size = le32_to_cpu(entry->e_value_size); + + if (size > XATTR_SIZE_MAX) + return -EFSCORRUPTED; + + if (size != 0 && entry->e_value_inum == 0) { u16 offs = le16_to_cpu(entry->e_value_offs); - u32 size = le32_to_cpu(entry->e_value_size); void *value; /* -- 2.16.2
