exec: Fix mem leak in kernel_read_file (CVE-2019-8980)

debian/changelog

@@ -632,6 +632,7 @@ linux (4.19.27-1) UNRELEASED; urgency=medium
   [ Salvatore Bonaccorso ]
   * Btrfs: fix corruption reading shared and compressed extents after hole
     punching (Closes: #922306)
+  * exec: Fix mem leak in kernel_read_file (CVE-2019-8980)
 
   [ Vagrant Cascadian ]
   * [arm64] Add patch from v4.20 to enable device-tree for Pine64-LTS.

debian/patches/bugfix/all/exec-Fix-mem-leak-in-kernel_read_file.patch

@@ -0,0 +1,50 @@
+From: YueHaibing <yuehaibing@huawei.com>
+Date: Tue, 19 Feb 2019 10:10:38 +0800
+Subject: exec: Fix mem leak in kernel_read_file
+Origin: https://git.kernel.org/linus/f612acfae86af7ecad754ae6a46019be9da05b8e
+Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2019-8980
+
+syzkaller report this:
+BUG: memory leak
+unreferenced object 0xffffc9000488d000 (size 9195520):
+  comm "syz-executor.0", pid 2752, jiffies 4294787496 (age 18.757s)
+  hex dump (first 32 bytes):
+    ff ff ff ff ff ff ff ff a8 00 00 00 01 00 00 00  ................
+    02 00 00 00 00 00 00 00 80 a1 7a c1 ff ff ff ff  ..........z.....
+  backtrace:
+    [<000000000863775c>] __vmalloc_node mm/vmalloc.c:1795 [inline]
+    [<000000000863775c>] __vmalloc_node_flags mm/vmalloc.c:1809 [inline]
+    [<000000000863775c>] vmalloc+0x8c/0xb0 mm/vmalloc.c:1831
+    [<000000003f668111>] kernel_read_file+0x58f/0x7d0 fs/exec.c:924
+    [<000000002385813f>] kernel_read_file_from_fd+0x49/0x80 fs/exec.c:993
+    [<0000000011953ff1>] __do_sys_finit_module+0x13b/0x2a0 kernel/module.c:3895
+    [<000000006f58491f>] do_syscall_64+0x147/0x600 arch/x86/entry/common.c:290
+    [<00000000ee78baf4>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
+    [<00000000241f889b>] 0xffffffffffffffff
+
+It should goto 'out_free' lable to free allocated buf while kernel_read
+fails.
+
+Fixes: 39d637af5aa7 ("vfs: forbid write access when reading a file into memory")
+Signed-off-by: YueHaibing <yuehaibing@huawei.com>
+Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
+---
+ fs/exec.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/fs/exec.c b/fs/exec.c
+index fb72d36f7823..bcf383730bea 100644
+--- a/fs/exec.c
++++ b/fs/exec.c
+@@ -932,7 +932,7 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
+ 		bytes = kernel_read(file, *buf + pos, i_size - pos, &pos);
+ 		if (bytes < 0) {
+ 			ret = bytes;
+-			goto out;
++			goto out_free;
+ 		}
+ 
+ 		if (bytes == 0)
+-- 
+2.20.1
+

debian/patches/series

@@ -143,6 +143,7 @@ features/all/lockdown/arm64-add-kernel-config-option-to-lock-down-when.patch
 
 # Security fixes
 debian/i386-686-pae-pci-set-pci-nobios-by-default.patch
+bugfix/all/exec-Fix-mem-leak-in-kernel_read_file.patch
 
 # Fix exported symbol versions
 bugfix/all/module-disable-matching-missing-version-crc.patch