linux-kernel - Re: [PATCH 1/1] security: introduce fs caps

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Date:	Tue, 14 Nov 2006 09:23:07 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	"Bill O'Donnell" <billodo@....com>
Cc:	"Serge E. Hallyn" <serue@...ibm.com>,
	Chris Friedhoff <chris@...edhoff.org>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Stephen Smalley <sds@...ho.nsa.gov>,
	James Morris <jmorris@...ei.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Andrew Morton <akpm@...l.org>,
	KaiGai Kohei <kaigai@...gai.gr.jp>,
	Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [PATCH 1/1] security: introduce fs caps

Quoting Bill O'Donnell (billodo@....com):
> 8102  execve("/sbin/setfcaps", ["setfcaps", "cap_net_raw=ep", "/bin/ping"], [/* 67 vars */]) = 0
> 8102  brk(0)                            = 0x6000000000004000
> 8102  uname({sys="Linux", node="certify", ...}) = 0
> 8102  access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
> 8102  open("/etc/ld.so.cache", O_RDONLY) = 3
> 8102  fstat(3, {st_mode=S_IFREG|0644, st_size=111415, ...}) = 0
> 8102  mmap(NULL, 111415, PROT_READ, MAP_PRIVATE, 3, 0) = 0x200000000004c000
> 8102  close(3)                          = 0
> 8102  open("/lib/libcap.so.1", O_RDONLY) = 3
> 8102  read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0002\0\1\0\0\0\340\25"..., 832) = 832
> 8102  fstat(3, {st_mode=S_IFREG|0755, st_size=22672, ...}) = 0
> 8102  mmap(NULL, 85800, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x2000000000068000
> 8102  madvise(0x2000000000068000, 85800, MADV_SEQUENTIAL|0x1) = 0
> 8102  mprotect(0x2000000000070000, 49152, PROT_NONE) = 0
> 8102  mmap(0x200000000007c000, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x4000) = 0x200000000007c000
> 8102  close(3)                          = 0
> 8102  open("/lib/libc.so.6.1", O_RDONLY) = 3
> 8102  read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0002\0\1\0\0\0\3609\2"..., 832) = 832
> 8102  fstat(3, {st_mode=S_IFREG|0755, st_size=2590313, ...}) = 0
> 8102  mmap(NULL, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2000000000080000
> 8102  mmap(NULL, 2416624, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x2000000000084000
> 8102  madvise(0x2000000000084000, 2416624, MADV_SEQUENTIAL|0x1) = 0
> 8102  mprotect(0x20000000002bc000, 49152, PROT_NONE) = 0
> 8102  mmap(0x20000000002c8000, 32768, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x234000) = 0x20000000002c8000
> 8102  mmap(0x20000000002d0000, 8176, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x20000000002d0000
> 8102  close(3)                          = 0
> 8102  mmap(NULL, 32768, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x20000000002d4000
> 8102  mmap(NULL, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x20000000002dc000
> 8102  munmap(0x200000000004c000, 111415) = 0
> 8102  brk(0)                            = 0x6000000000004000
> 8102  brk(0x6000000000028000)           = 0x6000000000028000
> 8102  capget(0x19980330, 0, {0, 0, 0})  = -1 EINVAL (Invalid argument)

I don't see why this capget is returning -EINVAL.  In fact I don't see
why it happens at all - cap_inode_setxattr would check
capable(CAP_SYS_ADMIN), but setxattr hasn't been called yet.  Looking at
both libcap and setfcaps.c, I don't see where the capget comes from.

As for the -EINVAL, kernel/capability.c:sys_capget() returns -EINVAL if
the _LINUX_CAPABILITY_VERSION is wrong - you have 0x19980330 which is
correct - if pid < 0 - but you send in 0 - or if security_capget
returns -EINVAL, which cap_capget (and dummy_capget) don't do.

Kaigai, do you have any ideas?

thanks,
-serge
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