On Mar 29, 2018, at 3:46 PM, Theodore Ts'o <tytso@xxxxxxx> wrote: > > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > ext4 isn't validating the sizes of xattrs. 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 <= INT_MAX bytes. Also add > explicit checks in ext4_xattr_block_get() and ext4_xattr_ibody_get() > just in case the xattr block is corrupted in memory. > > This issue has been assigned CVE-2018-1095. > > https://bugzilla.kernel.org/show_bug.cgi?id=199185 > https://bugzilla.redhat.com/show_bug.cgi?id=1560793 > > Reported-by: Wen Xu <wen.xu@xxxxxxxxxx> > Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> > Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > --- > fs/ext4/xattr.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c > index 63656dbafdc4..fea1108c3bea 100644 > --- a/fs/ext4/xattr.c > +++ b/fs/ext4/xattr.c > @@ -201,6 +201,9 @@ ext4_xattr_check_entries(struct ext4_xattr_entry *entry, void *end, > u32 size = le32_to_cpu(entry->e_value_size); > void *value; > > + if (size > INT_MAX) > + return -EFSCORRUPTED; > + > /* > * The value cannot overlap the names, and the value > * with padding cannot extend beyond 'end'. Check both > @@ -523,8 +526,10 @@ ext4_xattr_block_get(struct inode *inode, int name_index, const char *name, > if (error) > goto cleanup; > size = le32_to_cpu(entry->e_value_size); > + error = -ERANGE; > + if (unlikely(size > INT_MAX)) > + goto cleanup; > if (buffer) { > - error = -ERANGE; > if (size > buffer_size) > goto cleanup; > if (entry->e_value_inum) { > @@ -572,8 +577,10 @@ ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name, > if (error) > goto cleanup; > size = le32_to_cpu(entry->e_value_size); > + error = -ERANGE; > + if (unlikely(size > INT_MAX)) > + goto cleanup; > if (buffer) { > - error = -ERANGE; > if (size > buffer_size) > goto cleanup; > if (entry->e_value_inum) { > -- > 2.16.1.72.g5be1f00a9a > Cheers, Andreas
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