Control: reassign -1 src:zfs-linux
On Fri, 2023-09-22 at 16:13 +0000, WHR wrote:
> Package: src:linux
> Version: 6.5.3-1
> Severity: normal
> X-Debbugs-Cc: msl0000023...@gmail.com, msl0000023...@gmail.com
>
>
> Taking executable file /usr/bin/ssh to demonstrate the issue:
>
> # which ssh
> /usr/bin/ssh
> # ssh
>
> usage: ssh [-46AaCfGgKkMNnqsTtVvXxYy] [-B bind_interface]
> [-b bind_address] [-c cipher_spec] [-D [bind_address:]port]
> [-E log_file] [-e escape_char] [-F configfile] [-I pkcs11]
> [-i identity_file] [-J [user@]host[:port]] [-L address]
> [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p
> port]
> [-Q query_option] [-R address] [-S ctl_path] [-W host:port]
> [-w local_tun[:remote_tun]] destination [command]
> # chattr +i /usr/bin/ssh
>
> # ssh
> Segmentation fault
>
>
> By trying to load the program via ld.so(1) with truss (actually strace), it
> shows that a mmap(2) call used to load the data segument failed due to EPERM:
>
> # truss -s 128 -f /lib/powerpc64-linux-gnu/ld64.so.1 /usr/bin/ssh
> execve("/lib/powerpc64-linux-gnu/ld64.so.1",
> ["/lib/powerpc64-linux-gnu/ld64.so.1", "/usr/bin/ssh"], 0x7fffc0380530 /* 29
> vars */) = 0
> brk(NULL) = 0x1000db60000
> openat(AT_FDCWD, "/usr/bin/ssh", O_RDONLY|O_CLOEXEC) = 3
> read(3,
> "\177ELF\2\2\1\0\0\0\0\0\0\0\0\0\0\3\0\25\0\0\0\1\0\0\0\0\0\22h\220\0\0\0\0\0\0\0@\0\0\0\0\0\22\4\330\0\0\0\1\0@\08\0\t\0@\0\35\0\34\0\0\0\6\0\0\0\4\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\1\370\0\0\0\0\0\0\1\370\0\0\0\0\0\0\0\10\0\0\0\3\0\0\0\4"...,
> 832) = 832
> mmap(NULL, 1259760, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
> 0) = 0x7fff93720000
> mprotect(0x7fff93830000, 65536, PROT_NONE) = 0
> mmap(0x7fff93840000, 131072, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x110000) = -1 EPERM (Operation not
> permitted)
> close(3) = 0
> writev(2, [{iov_base="/usr/bin/ssh", iov_len=12}, {iov_base=": ",
> iov_len=2}, {iov_base="error while loading shared libraries", iov_len=36},
> {iov_base=": ", iov_len=2}, {iov_base="/usr/bin/ssh", iov_len=12},
> {iov_base=": ", iov_len=2}, {iov_base="failed to map segment from shared
> object", iov_len=40}, {iov_base="", iov_len=0}, {iov_base="", iov_len=0},
> {iov_base="\n", iov_len=1}], 10/usr/bin/ssh: error while loading shared
> libraries: /usr/bin/ssh: failed to map segment from shared object
> ) = 107
> exit_group(127) = ?
> +++ exited with 127 +++
>
>
> I can also reproduce this issue on Bullseye (with Linux 5.10.0-21-amd64);
> while Buster (Linux 4.19.0-23-amd64) is fine.
[...]
> ** Command line:
> root=ZFS=zr/ROOT/debiansid-be ro quiet
> cgroup_enable=cpuset,cpu,cpuacct,blkio,memory,devices,freezer,net_cls,perf_event,net_prio
> systemd.unified_cgroup_hierarchy=0
> net.ifname-policy=keep,onboard,slot,path,kernel zfs.zfs_txg_timeout=60
> zfs.zfs_arc_max=2166172771 init=/init
[...]I can't reproduce this on an ext4 filesystem, so I think ZFS is the problem. ZFS has its own check that blocks a writable mmap of an immutable file, without taking MAP_PRIVATE into account: https://sources.debian.org/src/zfs-linux/2.1.12-2/module/os/linux/zfs/zfs_vnops_os.c/#L3908 Ben. -- Ben Hutchings It is easier to change the specification to fit the program than vice versa.
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