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kernel/relay.c: handle alloc_percpu returning NULL in relay_open (CVE-2019-19462)

This commit is contained in:
Salvatore Bonaccorso 2020-06-05 12:29:55 +02:00
parent 7fc7c96d6e
commit 50bf5b3b3d
3 changed files with 74 additions and 0 deletions
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2
debian/changelog vendored
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@ -12,6 +12,8 @@ linux (4.19.118-2+deb10u1) UNRELEASED; urgency=medium
* netlabel: cope with NULL catmap (CVE-2020-10711)
* fs/binfmt_elf.c: allocate initialized memory in fill_thread_core_info()
(CVE-2020-10732)
* kernel/relay.c: handle alloc_percpu returning NULL in relay_open
(CVE-2019-19462)
-- Salvatore Bonaccorso <carnil@debian.org> Thu, 28 May 2020 23:02:30 +0200

71
debian/patches/bugfix/all/kernel-relay.c-handle-alloc_percpu-returning-NULL-in.patch vendored Normal file
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@ -0,0 +1,71 @@
From: Daniel Axtens <dja@axtens.net>
Date: Thu, 4 Jun 2020 16:51:27 -0700
Subject: kernel/relay.c: handle alloc_percpu returning NULL in relay_open
Origin: https://git.kernel.org/linus/54e200ab40fc14c863bcc80a51e20b7906608fce
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2019-19462
alloc_percpu() may return NULL, which means chan->buf may be set to NULL.
In that case, when we do *per_cpu_ptr(chan->buf, ...), we dereference an
invalid pointer:
BUG: Unable to handle kernel data access at 0x7dae0000
Faulting instruction address: 0xc0000000003f3fec
...
NIP relay_open+0x29c/0x600
LR relay_open+0x270/0x600
Call Trace:
relay_open+0x264/0x600 (unreliable)
__blk_trace_setup+0x254/0x600
blk_trace_setup+0x68/0xa0
sg_ioctl+0x7bc/0x2e80
do_vfs_ioctl+0x13c/0x1300
ksys_ioctl+0x94/0x130
sys_ioctl+0x48/0xb0
system_call+0x5c/0x68
Check if alloc_percpu returns NULL.
This was found by syzkaller both on x86 and powerpc, and the reproducer
it found on powerpc is capable of hitting the issue as an unprivileged
user.
Fixes: 017c59c042d0 ("relay: Use per CPU constructs for the relay channel buffer pointers")
Reported-by: syzbot+1e925b4b836afe85a1c6@syzkaller-ppc64.appspotmail.com
Reported-by: syzbot+587b2421926808309d21@syzkaller-ppc64.appspotmail.com
Reported-by: syzbot+58320b7171734bf79d26@syzkaller.appspotmail.com
Reported-by: syzbot+d6074fb08bdb2e010520@syzkaller.appspotmail.com
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Akash Goel <akash.goel@intel.com>
Cc: Andrew Donnellan <ajd@linux.ibm.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Salvatore Bonaccorso <carnil@debian.org>
Cc: <stable@vger.kernel.org> [4.10+]
Link: http://lkml.kernel.org/r/20191219121256.26480-1-dja@axtens.net
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
kernel/relay.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/relay.c b/kernel/relay.c
index 90c7a002436d..dc82705e1cff 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -581,6 +581,11 @@ struct rchan *relay_open(const char *base_filename,
return NULL;
chan->buf = alloc_percpu(struct rchan_buf *);
+ if (!chan->buf) {
+ kfree(chan);
+ return NULL;
+ }
+
chan->version = RELAYFS_CHANNEL_VERSION;
chan->n_subbufs = n_subbufs;
chan->subbuf_size = subbuf_size;
--
2.27.0.rc0

1
debian/patches/series vendored
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@ -308,5 +308,6 @@ bugfix/all/scsi-sg-add-sg_remove_request-in-sg_write.patch
bugfix/all/usb-gadget-fix-illegal-array-access-in-binding-with-.patch
bugfix/all/netlabel-cope-with-NULL-catmap.patch
bugfix/all/fs-binfmt_elf.c-allocate-initialized-memory-in-fill_.patch
bugfix/all/kernel-relay.c-handle-alloc_percpu-returning-NULL-in.patch
# ABI maintenance