Hello, just found a bug in selinux.
Whats going wrong:
Copy a link with "-a" option while selinux is on.
steps to reproduce:
~$ mkdir -p a/b
~$ ln -s b a/c
~$ cp -a a b
cp: failed to restore the default file creation context: Invalid argument
Results of my investigation:
The "cp" of coreutils is calling "setfscreatecon (NULL)" to restore the
default file creation context (coreutils-8.30/src/copy.c:1771) as it is
stated in the selinux api (/libselinux/include/selinux/selinux.h:71).
As we see in the result of strace below, the kernel returns an -1 on try
to restore the default file creation context. So in my opinion is the
bug has to be in the selinux_setprocattr method in the
security/selinux/hooks.c file.
Part of "strace cp -a a b"
lgetxattr("a/c", "security.selinux", "system_u:object_r:user_home_dir_t:s0",
255) = 37
readlink("a/c", "b", 2) = 1
symlink("b", "b/a/c") = 0
open("/proc/self/task/2136/attr/fscreate", O_RDWR|O_CLOEXEC) = 3
write(3, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0
open("/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=2995, ...}) = 0
read(3, "# Locale name alias data base.\n#"..., 4096) = 2995
read(3, "", 4096) = 0
close(3)
** Description changed:
- come later
+ Hello, just found a bug in selinux.
+
+ Whats going wrong:
+
+ Copy a link with "-a" option while selinux is on.
+
+ steps to reproduce:
+
+ ~$ mkdir -p a/b
+ ~$ ln -s b a/c
+ ~$ cp -a a b
+ cp: failed to restore the default file creation context: Invalid argument
+
+ Results of my investigation:
+
+ The "cp" of coreutils is calling "setfscreatecon (NULL)" to restore the
+ default file creation context (coreutils-8.30/src/copy.c:1771) as it is
+ stated in the selinux api (/libselinux/include/selinux/selinux.h:71).
+
+ As we see in the result of strace below, the kernel returns an -1 on try
+ to restore the default file creation context. So in my opinion is the
+ bug has to be in the selinux_setprocattr method in the
+ security/selinux/hooks.c file.
+
+ Part of "strace cp -a a b"
+
+ lgetxattr("a/c", "security.selinux", "system_u:object_r:user_home_dir_t:s0",
255) = 37
+ readlink("a/c", "b", 2) = 1
+ symlink("b", "b/a/c") = 0
+ open("/proc/self/task/2136/attr/fscreate", O_RDWR|O_CLOEXEC) = 3
+ write(3, NULL, 0) = -1 EINVAL (Invalid argument)
+ close(3) = 0
+ open("/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3
+ fstat(3, {st_mode=S_IFREG|0644, st_size=2995, ...}) = 0
+ read(3, "# Locale name alias data base.\n#"..., 4096) = 2995
+ read(3, "", 4096) = 0
+ close(3)
** Changed in: linux (Ubuntu)
Status: Incomplete => Confirmed
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https://bugs.launchpad.net/bugs/1794067
Title:
Bug in selinux on ubuntu 16.04 with kernel 4.15.0-34
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