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authorJiri Slaby <jslaby@suse.cz>2018-01-12 17:34:16 +0100
committerJiri Slaby <jslaby@suse.cz>2018-01-14 16:53:08 +0100
commite1fc2a6b15657d349e7cdd5929fa71356b43d50a (patch)
tree783f5939593f87835732a79a507a88a0bc72cdd3
parentffda3e4d8bc8639de14963e2f54bbcd087127341 (diff)
bpf, array: fix overflow in max_entries and undefined behaviorrpm-4.12.14-8
in index_mask (bsc#1068032 CVE-2017-5753).
-rw-r--r--patches.suse/bpf-array-fix-overflow-in-max_entries-and-undefined-.patch79
-rw-r--r--series.conf1
2 files changed, 80 insertions, 0 deletions
diff --git a/patches.suse/bpf-array-fix-overflow-in-max_entries-and-undefined-.patch b/patches.suse/bpf-array-fix-overflow-in-max_entries-and-undefined-.patch
new file mode 100644
index 0000000000..1e27f4bb82
--- /dev/null
+++ b/patches.suse/bpf-array-fix-overflow-in-max_entries-and-undefined-.patch
@@ -0,0 +1,79 @@
+From: Daniel Borkmann <daniel@iogearbox.net>
+Date: Wed, 10 Jan 2018 23:25:05 +0100
+Subject: bpf, array: fix overflow in max_entries and undefined behavior in
+ index_mask
+Patch-mainline: Queued in subsystem maintainer repository
+Git-commit: bbeb6e4323dad9b5e0ee9f60c223dd532e2403b1
+Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git
+References: bsc#1068032 CVE-2017-5753
+
+syzkaller tried to alloc a map with 0xfffffffd entries out of a userns,
+and thus unprivileged. With the recently added logic in b2157399cc98
+("bpf: prevent out-of-bounds speculation") we round this up to the next
+power of two value for max_entries for unprivileged such that we can
+apply proper masking into potentially zeroed out map slots.
+
+However, this will generate an index_mask of 0xffffffff, and therefore
+a + 1 will let this overflow into new max_entries of 0. This will pass
+allocation, etc, and later on map access we still enforce on the original
+attr->max_entries value which was 0xfffffffd, therefore triggering GPF
+all over the place. Thus bail out on overflow in such case.
+
+Moreover, on 32 bit archs roundup_pow_of_two() can also not be used,
+since fls_long(max_entries - 1) can result in 32 and 1UL << 32 in 32 bit
+space is undefined. Therefore, do this by hand in a 64 bit variable.
+
+This fixes all the issues triggered by syzkaller's reproducers.
+
+Fixes: b2157399cc98 ("bpf: prevent out-of-bounds speculation")
+Reported-by: syzbot+b0efb8e572d01bce1ae0@syzkaller.appspotmail.com
+Reported-by: syzbot+6c15e9744f75f2364773@syzkaller.appspotmail.com
+Reported-by: syzbot+d2f5524fb46fd3b312ee@syzkaller.appspotmail.com
+Reported-by: syzbot+61d23c95395cc90dbc2b@syzkaller.appspotmail.com
+Reported-by: syzbot+0d363c942452cca68c01@syzkaller.appspotmail.com
+Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
+Signed-off-by: Alexei Starovoitov <ast@kernel.org>
+Signed-off-by: Jiri Slaby <jslaby@suse.cz>
+---
+ kernel/bpf/arraymap.c | 18 +++++++++++++++---
+ 1 file changed, 15 insertions(+), 3 deletions(-)
+
+--- a/kernel/bpf/arraymap.c
++++ b/kernel/bpf/arraymap.c
+@@ -52,7 +52,7 @@ static struct bpf_map *array_map_alloc(u
+ u32 elem_size, index_mask, max_entries;
+ bool unpriv = !capable(CAP_SYS_ADMIN);
+ struct bpf_array *array;
+- u64 array_size;
++ u64 array_size, mask64;
+
+ /* check sanity of attributes */
+ if (attr->max_entries == 0 || attr->key_size != 4 ||
+@@ -68,13 +68,25 @@ static struct bpf_map *array_map_alloc(u
+ elem_size = round_up(attr->value_size, 8);
+
+ max_entries = attr->max_entries;
+- index_mask = roundup_pow_of_two(max_entries) - 1;
+
+- if (unpriv)
++ /* On 32 bit archs roundup_pow_of_two() with max_entries that has
++ * upper most bit set in u32 space is undefined behavior due to
++ * resulting 1U << 32, so do it manually here in u64 space.
++ */
++ mask64 = fls_long(max_entries - 1);
++ mask64 = 1ULL << mask64;
++ mask64 -= 1;
++
++ index_mask = mask64;
++ if (unpriv) {
+ /* round up array size to nearest power of 2,
+ * since cpu will speculate within index_mask limits
+ */
+ max_entries = index_mask + 1;
++ /* Check for overflows. */
++ if (max_entries < attr->max_entries)
++ return ERR_PTR(-E2BIG);
++ }
+
+ array_size = sizeof(*array);
+ if (percpu)
diff --git a/series.conf b/series.conf
index fae2bcaebd..7cab5648c4 100644
--- a/series.conf
+++ b/series.conf
@@ -1066,6 +1066,7 @@
patches.suse/0017-userns-prevent-speculative-execution.patch
patches.suse/bpf-prevent-out-of-bounds-speculation.patch
+ patches.suse/bpf-array-fix-overflow-in-max_entries-and-undefined-.patch
########################################################
# locking/core