LDP
/
man-pages
mirror of https://github.com/mkerrisk/man-pages
0
1
Fork 0
Code Releases Activity

prctl.2: Greatly expand discussion of "dumpable" flag 

In particular, detail the interactions with
/proc/sys/fs/suid_dumpable.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2015-01-19 14:36:59 +01:00
parent 6e2bb1c2f7
commit 2d7fc98dfe
1 changed files with 47 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
man2/prctl.2
View File

@ -137,9 +137,9 @@ in the location pointed to by
.IR "(int\ *) arg2" .
.TP
.BR PR_SET_DUMPABLE " (since Linux 2.3.20)"
Set the state of the flag determining whether core dumps are produced
for the calling process upon delivery of a signal whose default behavior is
to produce a core dump.
Set the state of the "dumpable" flag,
which determines whether core dumps are produced for the calling process
upon delivery of a signal whose default behavior is to produce a core dump.
In kernels up to and including 2.6.12,
.I arg2
@ -159,17 +159,53 @@ for security reasons, this feature has been removed.
.\" From: Marcel Holtmann <marcel () holtmann ! org>
.\" Date: 2006-07-12 11:12:00
(See also the description of
.I /proc/sys/fs/suid_dumpable
.I /proc/sys/fs/\:suid_dumpable
in
.BR proc (5).)
Normally, this flag is set for a process by default, but it is cleared
when a set-user-ID or set-group-ID program,
or a program that has file capabilities associated with it (see
.BR capabilities (7)),
is executed.
It is also set by various system calls that manipulate process UIDs and GIDs.
Normally, this flag is set to 1.
However, it is reset to the current value contained in the file
.IR /proc/sys/fs/\:suid_dumpable
(which by default has the value 0),
if any of the following attributes of the process
are changed by the operations listed below:
.\" See kernel/cred.c::commit_creds() (Linux 3.18 sources)
.RS
.IP * 3
The effective user or group ID is changed.
.IP *
The filesystem user or group ID is changed (see
.BR credentials (7)).
.IP *
The process's set of permitted capabilities (see
.BR capabilities (7))
is changed such that its new set of capabilities is
not a subset of its previous set of capabilities.
.RE
.IP
The operations that may trigger changes to the dumpable flag include:
.\" Look for uses of commit_creds() in the kernel source code
.RS
.IP * 3
execution
.RB ( execve (2))
of a set-user-ID or set-group-ID program,
or a program that has capabilities (see
.BR capabilities (7));
.IP *
.BR capset (2);
and
.IP *
system calls that change process credentials
.RB ( setuid (2)
.BR setgid (2),
.BR setresuid (2),
.BR setresgid (2),
.BR setgroups (2),
and so on).
.\" Also certain namespace operations;
.RE
.IP
Processes that are not dumpable can not be attached via
.BR ptrace (2)
.BR PTRACE_ATTACH .