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SubjectRe: Is CAP_SYS_ADMIN checked by every program !?
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Date
Hello,

Bernd Eckenfels wrote:
> You can add dump_stack(void) from kernel.h to you patch, since there are not
> many sources for SYS_ADMIN capabilities checks in the kernel. You will
> quickly find the syscall in question.

Oh, this is exactly what I need.

And the following is the results of these tow lines.
printk("\n[%s]\n", current->comm);
dump_stack();

[ls]
[<c01e1852>] cap_vm_enough_memory+0x82/0x1f0
[<c0156dcd>] setup_arg_pages+0x9d/0x230
[<c0174373>] load_elf_binary+0x473/0xca0
[<c01334e7>] __alloc_pages+0xa7/0x360
[<c0156bdd>] copy_strings+0x1dd/0x200
[<c0157b00>] search_binary_handler+0x50/0x170
[<c0157d9e>] do_execve+0x17e/0x210
[<c01010bc>] sys_execve+0x3c/0x80
[<c010246d>] sysenter_past_esp+0x52/0x75

[cat]
[<c01e1852>] cap_vm_enough_memory+0x82/0x1f0
[<c0156dcd>] setup_arg_pages+0x9d/0x230
[<c0174373>] load_elf_binary+0x473/0xca0
[<c01334e7>] __alloc_pages+0xa7/0x360
[<c0156bdd>] copy_strings+0x1dd/0x200
[<c0157b00>] search_binary_handler+0x50/0x170
[<c0157d9e>] do_execve+0x17e/0x210
[<c01010bc>] sys_execve+0x3c/0x80
[<c010246d>] sysenter_past_esp+0x52/0x75

[tcsh]
[<c01e1852>] cap_vm_enough_memory+0x82/0x1f0
[<c0112c1e>] copy_mm+0x17e/0x360
[<c0113686>] copy_process+0x406/0x9c0
[<c0113d45>] do_fork+0x75/0x1ad
[<c01e753e>] copy_to_user+0x3e/0x50
[<c011f85e>] sys_rt_sigprocmask+0xae/0x100
[<c010103c>] sys_clone+0x3c/0x40
[<c010246d>] sysenter_past_esp+0x52/0x75

[sed]
[<c01e1852>] cap_vm_enough_memory+0x82/0x1f0
[<c0156dcd>] setup_arg_pages+0x9d/0x230
[<c0174373>] load_elf_binary+0x473/0xca0
[<c01334e7>] __alloc_pages+0xa7/0x360
[<c0156bdd>] copy_strings+0x1dd/0x200
[<c0157b00>] search_binary_handler+0x50/0x170
[<c0157d9e>] do_execve+0x17e/0x210
[<c01010bc>] sys_execve+0x3c/0x80
[<c010246d>] sysenter_past_esp+0x52/0x75

[klogd]
[<c01e179c>] cap_syslog+0x4c/0x80
[<c011445d>] do_syslog+0x2d/0x380
[<c0127640>] autoremove_wake_function+0x0/0x60
[<c011cb84>] update_process_times+0x44/0x50
[<c0127640>] autoremove_wake_function+0x0/0x60
[<c014cda6>] vfs_read+0x116/0x160
[<c014d0b1>] sys_read+0x51/0x80
[<c010246d>] sysenter_past_esp+0x52/0x75

The function which calls capable(CAP_SYS_ADMIN) is
cap_vm_enough_memory() defined in security/commoncap.c ,
and this function is called whenever sys_execve() is called.
Therefore, it seemed to me that every program calls capable(CAP_SYS_ADMIN).

Thank you very much.
--
Tetsuo Handa
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