[screen-devel] [bug #55618] Closing half a million file descriptors on startup

[Lukas Waymann]

URL:
  <https://savannah.gnu.org/bugs/?55618>

                 Summary: Closing half a million file descriptors on startup
                 Project: GNU Screen
            Submitted by: meribold
            Submitted on: Thu 31 Jan 2019 03:30:40 PM UTC
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                 Release: None
           Fixed Release: None
         Planned Release: None
           Work Required: None

    _______________________________________________________

Details:

systemd recently increased the default hard limit of how many simultaneous
file descriptors unprivileged user space processes can have
(HIGH_RLIMIT_NOFILE?).  First to 262144 [1] and later to 524288 [2]. 
Apparently from 4096 (Linux default?).

It seems that this causes screen to try to close half a million file
descriptors on startup.  Here's the strace of `screen --version` (abridged;
the whole thing is 37 MiB):


execve("/usr/bin/screen", ["screen", "--version"], 0x7ffe6fae1658 /* 43 vars
*/) = 0
access("/etc/suid-debug", F_OK) = -1 ENOENT (No such file or directory)
brk(NULL) = 0x5570a6a60000
arch_prctl(0x3001 /* ARCH_??? */, 0x7ffc8551a8c0) = -1 EINVAL (Invalid
argument)
fcntl(0, F_GETFD) = 0
fcntl(1, F_GETFD) = 0
fcntl(2, F_GETFD) = 0
access("/etc/suid-debug", F_OK) = -1 ENOENT (No such file or directory)
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=232430, ...}) = 0
mmap(NULL, 232430, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fa20bd14000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/tls/x86_64/x86_64/libtinfo.so.6",
O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat("/usr/lib/tls/x86_64/x86_64", 0x7ffc85519b00) = -1 ENOENT (No such file
or directory)
openat(AT_FDCWD, "/usr/lib/tls/x86_64/libtinfo.so.6", O_RDONLY|O_CLOEXEC) = -1
ENOENT (No such file or directory)
stat("/usr/lib/tls/x86_64", 0x7ffc85519b00) = -1 ENOENT (No such file or
directory)
openat(AT_FDCWD, "/usr/lib/tls/x86_64/libtinfo.so.6", O_RDONLY|O_CLOEXEC) = -1
ENOENT (No such file or directory)
stat("/usr/lib/tls/x86_64", 0x7ffc85519b00) = -1 ENOENT (No such file or
directory)
openat(AT_FDCWD, "/usr/lib/tls/libtinfo.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT
(No such file or directory)
stat("/usr/lib/tls", 0x7ffc85519b00) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/x86_64/x86_64/libtinfo.so.6", O_RDONLY|O_CLOEXEC) =
-1 ENOENT (No such file or directory)
stat("/usr/lib/x86_64/x86_64", 0x7ffc85519b00) = -1 ENOENT (No such file or
directory)
openat(AT_FDCWD, "/usr/lib/x86_64/libtinfo.so.6", O_RDONLY|O_CLOEXEC) = -1
ENOENT (No such file or directory)
stat("/usr/lib/x86_64", 0x7ffc85519b00) = -1 ENOENT (No such file or
directory)
openat(AT_FDCWD, "/usr/lib/x86_64/libtinfo.so.6", O_RDONLY|O_CLOEXEC) = -1
ENOENT (No such file or directory)
stat("/usr/lib/x86_64", 0x7ffc85519b00) = -1 ENOENT (No such file or
directory)
openat(AT_FDCWD, "/usr/lib/libtinfo.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0 p\1\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=449040, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x7fa20bd12000
mmap(NULL, 453880, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) =
0x7fa20bca3000
mmap(0x7fa20bcba000, 241664, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x17000) = 0x7fa20bcba000
mmap(0x7fa20bcf5000, 94208, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3,
0x52000) = 0x7fa20bcf5000
mmap(0x7fa20bd0c000, 24576, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x68000) = 0x7fa20bd0c000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/libcrypt.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0 \20\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=42912, ...}) = 0
mmap(NULL, 233824, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) =
0x7fa20bc69000
mprotect(0x7fa20bc6a000, 36864, PROT_NONE) = 0
mmap(0x7fa20bc6a000, 24576, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1000) = 0x7fa20bc6a000
mmap(0x7fa20bc70000, 8192, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3,
0x7000) = 0x7fa20bc70000
mmap(0x7fa20bc73000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x9000) = 0x7fa20bc73000
mmap(0x7fa20bc75000, 184672, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fa20bc75000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/libpam.so.0", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0`\"\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=55048, ...}) = 0
mmap(NULL, 2150416, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) =
0x7fa20ba5b000
mprotect(0x7fa20ba68000, 2093056, PROT_NONE) = 0
mmap(0x7fa20bc67000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xc000) = 0x7fa20bc67000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0000C\2\0\0\0\0\0"...,
832) = 832
lseek(3, 792, SEEK_SET) = 792
read(3,
"\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\201\336\t\36\251c\324\233E\371SoK\5H\334"...,
68) = 68
fstat(3, {st_mode=S_IFREG|0755, st_size=2136840, ...}) = 0
lseek(3, 792, SEEK_SET) = 792
read(3,
"\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\201\336\t\36\251c\324\233E\371SoK\5H\334"...,
68) = 68
lseek(3, 864, SEEK_SET) = 864
read(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0",
32) = 32
mmap(NULL, 1848896, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) =
0x7fa20b897000
mprotect(0x7fa20b8b9000, 1671168, PROT_NONE) = 0
mmap(0x7fa20b8b9000, 1355776, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7fa20b8b9000
mmap(0x7fa20ba04000, 311296, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE,
3, 0x16d000) = 0x7fa20ba04000
mmap(0x7fa20ba51000, 24576, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1b9000) = 0x7fa20ba51000
mmap(0x7fa20ba57000, 13888, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fa20ba57000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/libdl.so.2", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0 \20\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=14240, ...}) = 0
mmap(NULL, 16528, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) =
0x7fa20b892000
mmap(0x7fa20b893000, 4096, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1000) = 0x7fa20b893000
mmap(0x7fa20b894000, 4096, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3,
0x2000) = 0x7fa20b894000
mmap(0x7fa20b895000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7fa20b895000
close(3) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x7fa20b890000
arch_prctl(ARCH_SET_FS, 0x7fa20b891000) = 0
mprotect(0x7fa20ba51000, 16384, PROT_READ) = 0
mprotect(0x7fa20b895000, 4096, PROT_READ) = 0
mprotect(0x7fa20bc67000, 4096, PROT_READ) = 0
mprotect(0x7fa20bc73000, 4096, PROT_READ) = 0
mprotect(0x7fa20bd0c000, 20480, PROT_READ) = 0
mprotect(0x5570a5ede000, 4096, PROT_READ) = 0
mprotect(0x7fa20bd76000, 4096, PROT_READ) = 0
munmap(0x7fa20bd14000, 232430) = 0
prlimit64(0, RLIMIT_NOFILE, NULL, {rlim_cur=1024, rlim_max=512*1024}) = 0
close(524287) = -1 EBADF (Bad file descriptor)
close(524286) = -1 EBADF (Bad file descriptor)
close(524285) = -1 EBADF (Bad file descriptor)
...
...
(This goes on.)
...
...
close(5) = -1 EBADF (Bad file descriptor)
close(4) = -1 EBADF (Bad file descriptor)
close(3) = -1 EBADF (Bad file descriptor)
brk(NULL) = 0x5570a6a60000
brk(0x5570a6a81000) = 0x5570a6a81000
getuid() = 1000
getgid() = 100
geteuid() = 1000
getegid() = 100
fstat(1, {st_mode=S_IFREG|0644, st_size=38279899, ...}) = 0
write(1, "Screen version 4.06.02 (GNU) 23-"..., 40Screen version 4.06.02 (GNU)
23-Oct-17
) = 40
exit_group(1) = ?
+++ exited with 1 +++


Also see <https://bugs.archlinux.org/task/61463>.

[1]:
https://github.com/systemd/systemd/commit/8aeb1d3176bf90f42c469deb40c3cfdda913acf2
[2]:
https://github.com/systemd/systemd/commit/09dad04c49cae3ad2b319c9b4e7773fedd34309a





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