| Message ID | 20200720091328.290336-13-mtk.manpages@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Manual pages: various fixes | expand |
I've applied all but this one. This one seems to imply that if the effective bit is lowered, but the permitted bits are raised, the ambient will have some sort of effect. This isn't how it works. Any file caps (even an empty set) suppresses any effect of the ambient vector. Cheers Andrew On Mon, Jul 20, 2020 at 2:14 AM Michael Kerrisk (man-pages) <mtk.manpages@gmail.com> wrote: > > The addition of Ambient capabilities in Linux 4.3 rendered the text on > the effect of the Effective bit during execve(2) out-of-date. Fix that. > Also add a couple of paragraph breaks to improve readability. > > Signed-off-by: Michael Kerrisk (man-pages) <mtk.manpages@gmail.com> > --- > doc/cap_get_file.3 | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/doc/cap_get_file.3 b/doc/cap_get_file.3 > index ceacbaf..dc7b571 100644 > --- a/doc/cap_get_file.3 > +++ b/doc/cap_get_file.3 > @@ -103,13 +103,18 @@ or > These functions are specified by withdrawn POSIX.1e draft specification. > .SH NOTES > Support for file capabilities is provided on Linux since version 2.6.24. > - > +.PP > On Linux, the file Effective set is a single bit. > If it is enabled, then all Permitted capabilities are enabled > in the Effective set of the calling process when the file is executed; > -otherwise, no capabilities are enabled in the process's Effective set > +otherwise, the process's Ambient capabilities > +(or, before the Linux 4.3 addition of Ambient capabilities, no capabilities) > +are enabled in the process's Effective set > following an > -.BR execve (2). > +.BR execve (2) > +(see > +.BR capabilities (7)). > +.PP > Because the file Effective set is a single bit, > if any capability is enabled in the Effective set of the > .I cap_t > -- > 2.26.2 >
Hi Andrew, On Mon, 20 Jul 2020 at 17:36, Andrew G. Morgan <morgan@kernel.org> wrote: > > I've applied all but this one. This one seems to imply that if the > effective bit is lowered, but the permitted bits are raised, the > ambient will have some sort of effect. This isn't how it works. Any > file caps (even an empty set) suppresses any effect of the ambient > vector. Thanks for catching that. I was trying to capture this piece of the execve() transformation rules: P'(effective) = F(effective) ? P'(permitted) : P'(ambient) But of course, I failed to capture the detail that it is the process's *new* ambient set (which, as you note, is cleared if the file has any attached capabilities) that is assigned to the effective set. Perhaps the text is best left as is. If I have some better idea, I'll come back to you. Thanks, Michael > On Mon, Jul 20, 2020 at 2:14 AM Michael Kerrisk (man-pages) > <mtk.manpages@gmail.com> wrote: > > > > The addition of Ambient capabilities in Linux 4.3 rendered the text on > > the effect of the Effective bit during execve(2) out-of-date. Fix that. > > Also add a couple of paragraph breaks to improve readability. > > > > Signed-off-by: Michael Kerrisk (man-pages) <mtk.manpages@gmail.com> > > --- > > doc/cap_get_file.3 | 11 ++++++++--- > > 1 file changed, 8 insertions(+), 3 deletions(-) > > > > diff --git a/doc/cap_get_file.3 b/doc/cap_get_file.3 > > index ceacbaf..dc7b571 100644 > > --- a/doc/cap_get_file.3 > > +++ b/doc/cap_get_file.3 > > @@ -103,13 +103,18 @@ or > > These functions are specified by withdrawn POSIX.1e draft specification. > > .SH NOTES > > Support for file capabilities is provided on Linux since version 2.6.24. > > - > > +.PP > > On Linux, the file Effective set is a single bit. > > If it is enabled, then all Permitted capabilities are enabled > > in the Effective set of the calling process when the file is executed; > > -otherwise, no capabilities are enabled in the process's Effective set > > +otherwise, the process's Ambient capabilities > > +(or, before the Linux 4.3 addition of Ambient capabilities, no capabilities) > > +are enabled in the process's Effective set > > following an > > -.BR execve (2). > > +.BR execve (2) > > +(see > > +.BR capabilities (7)). > > +.PP > > Because the file Effective set is a single bit, > > if any capability is enabled in the Effective set of the > > .I cap_t > > -- > > 2.26.2 > >
diff --git a/doc/cap_get_file.3 b/doc/cap_get_file.3 index ceacbaf..dc7b571 100644 --- a/doc/cap_get_file.3 +++ b/doc/cap_get_file.3 @@ -103,13 +103,18 @@ or These functions are specified by withdrawn POSIX.1e draft specification. .SH NOTES Support for file capabilities is provided on Linux since version 2.6.24. - +.PP On Linux, the file Effective set is a single bit. If it is enabled, then all Permitted capabilities are enabled in the Effective set of the calling process when the file is executed; -otherwise, no capabilities are enabled in the process's Effective set +otherwise, the process's Ambient capabilities +(or, before the Linux 4.3 addition of Ambient capabilities, no capabilities) +are enabled in the process's Effective set following an -.BR execve (2). +.BR execve (2) +(see +.BR capabilities (7)). +.PP Because the file Effective set is a single bit, if any capability is enabled in the Effective set of the .I cap_t
The addition of Ambient capabilities in Linux 4.3 rendered the text on the effect of the Effective bit during execve(2) out-of-date. Fix that. Also add a couple of paragraph breaks to improve readability. Signed-off-by: Michael Kerrisk (man-pages) <mtk.manpages@gmail.com> --- doc/cap_get_file.3 | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)