I have so far successfully used dmesg with (more or less) regular user permssions (with the exception of
some special group memberships like disk, audio).
Something in a recent upgrade changed dmesg's behavior and now I need to become root to run it successfully.
Otherwise i get
sts@nbof16:/var/log$ dmesg
dmesg: read kernel buffer failed: Operation not permitted
My intention is to restore the original behavior.
I checked the changelog.Debian of util-linux without finding a hint what as changed and how to revert it.
The strace of dmesg looks unsuspicous to me, but maybe somebody is able to find the rough spot (see attachment).
FYI - I follow testing with the exception of the kernel, which is linux-image-4.8.0-1-amd64
Code: Select all
sts@nbof16:/var/log$ cat /tmp/out
execve("/bin/dmesg", ["dmesg"], [/* 59 vars */]) = 0
brk(NULL) = 0x24aa000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap(NULL, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fc678ecf000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=326086, ...}) = 0
mmap(NULL, 326086, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fc678e7f000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libtinfo.so.5", 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`\315\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=170776, ...}) = 0
mmap(NULL, 2267936, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fc678a86000
mprotect(0x7fc678aab000, 2097152, PROT_NONE) = 0
mmap(0x7fc678cab000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x25000) = 0x7fc678cab000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/librt.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\340 \0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=31744, ...}) = 0
mmap(NULL, 2128832, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fc67887e000
mprotect(0x7fc678885000, 2093056, PROT_NONE) = 0
mmap(0x7fc678a84000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6000) = 0x7fc678a84000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/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\0\320\3\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1685264, ...}) = 0
mmap(NULL, 3791264, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fc6784e0000
mprotect(0x7fc678675000, 2093056, PROT_NONE) = 0
mmap(0x7fc678874000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x194000) = 0x7fc678874000
mmap(0x7fc67887a000, 14752, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fc67887a000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libpthread.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\340`\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=135448, ...}) = 0
mmap(NULL, 2212904, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fc6782c3000
mprotect(0x7fc6782db000, 2093056, PROT_NONE) = 0
mmap(0x7fc6784da000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x17000) = 0x7fc6784da000
mmap(0x7fc6784dc000, 13352, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fc6784dc000
close(3) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fc678e7d000
arch_prctl(ARCH_SET_FS, 0x7fc678e7e040) = 0
mprotect(0x7fc678874000, 16384, PROT_READ) = 0
mprotect(0x7fc6784da000, 4096, PROT_READ) = 0
mprotect(0x7fc678a84000, 4096, PROT_READ) = 0
mprotect(0x7fc678cab000, 16384, PROT_READ) = 0
mprotect(0x60b000, 4096, PROT_READ) = 0
mprotect(0x7fc678ed2000, 4096, PROT_READ) = 0
munmap(0x7fc678e7f000, 326086) = 0
set_tid_address(0x7fc678e7e310) = 9449
set_robust_list(0x7fc678e7e320, 24) = 0
rt_sigaction(SIGRTMIN, {0x7fc6782c8b80, [], SA_RESTORER|SA_SIGINFO, 0x7fc6782d4100}, NULL, 8) = 0
rt_sigaction(SIGRT_1, {0x7fc6782c8c10, [], SA_RESTORER|SA_RESTART|SA_SIGINFO, 0x7fc6782d4100}, NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
getrlimit(RLIMIT_STACK, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
brk(NULL) = 0x24aa000
brk(0x24cb000) = 0x24cb000
open("/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=3234528, ...}) = 0
mmap(NULL, 3234528, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fc677fad000
close(3) = 0
ioctl(1, TCGETS, 0x7fff5f162370) = -1 ENOTTY (Inappropriate ioctl for device)
open("/dev/kmsg", O_RDONLY|O_NONBLOCK) = -1 EPERM (Operation not permitted)
syslog(SYSLOG_ACTION_SIZE_BUFFER, NULL, 0) = -1 EPERM (Operation not permitted)
syslog(SYSLOG_ACTION_READ_ALL, 0x24ab0e0, 16392) = -1 EPERM (Operation not permitted)
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) = 0
open("/usr/share/locale/en_US/LC_MESSAGES/util-linux.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/util-linux.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, "dmesg: ", 7dmesg: ) = 7
write(2, "read kernel buffer failed", 25read kernel buffer failed) = 25
write(2, ": ", 2: ) = 2
open("/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, "Operation not permitted\n", 24Operation not permitted
) = 24
close(1) = 0
close(2) = 0
exit_group(1) = ?
+++ exited with 1 +++ 
