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From a57eb14b740e6175aff8b8941bec628403992dfa Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Thu, 29 Mar 2018 14:31:42 -0400
Subject: [PATCH] ext4: limit xattr size to INT_MAX
commit ce3fd194fcc6fbdc00ce095a852f22df97baa401 upstream.
ext4 isn't validating the sizes of xattrs where the value of the xattr
is stored in an external inode. 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.
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
CVE: CVE-2018-1095
Upstream-Status: Backport [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=a57eb14b740e6175aff8b8941bec628403992dfa]
Reported-by: Wen Xu <wen.xu@gatech.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Fixes: e50e5129f384 ("ext4: xattr-in-inode support")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
---
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 218a7ba57819..5d0f5ba5c6f5 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -194,10 +194,13 @@ 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 > INT_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;
/*
--
2.20.1
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