On 09.09.2014 0:28, Patrick Kelsey wrote: > In r268997, _ftello() was modified to use _fcntl(F_GETFL) in the > non-append, write-only path. Consequently, programs that use _ftello() > (via ftell, fgetpos, fsetpos, fseek, rewind...) on non-append, > write-only files and that use capsicum to restrict capabilities on the > associated fds to [CAP_SEEK, CAP_WRITE] broke as all ftell() (and > friends) calls on those files fail with ENOTCAPABLE due to lack of > CAP_FCNTL rights. There appear to be only two affected programs in the > tree - tcpdump and dhclient. This affects both CURRENT and 10-STABLE > (including 10.1-PRERELEASE) > > tcpdump, when configured to write to capture files rotated by size, > fails to rotate and captures indefinitely to the first file in the > series. This can be reproduced by a command such as: tcpdump -i > <ifname> -C 1 -W 2 -w packets -v > > By inspection, dhclient will fail to trim old data from its client > leases file when rewriting that file with a lesser amount of data than > it currently contains. See the ftruncate() call in > dhclient.c:rewrite_client_leases(). > > The attached patch adds CAP_FCNTL to the limited rights established for > non-append, write-only files used by tcpdump and dhclient. It also > restricts the fcntl rights to CAP_FCNTL_GETFL. > > The current need to have CAP_FCNTL rights in order to get or set the > file position on non-append, write-only files is subtle. Perhaps part > of the answer is to define a CAP_FSEEK right in sys/capability.h that > resolves to CAP_SEEK|CAP_FCNTL, or to modify the CAP_SEEK description in > rights(4) to note the need for CAP_FCNTL when using ftell() and friends. > > -Patrick
Stdio code use fcntl(F_GETFL) already in many places, f.e. fdopen(), freopen(). libc code in general use it in rpc code. According to your note, all that places are currently broken in anyway. I don't think that this read-only fcntl(F_GETFL) which doesn not modify anything deserves any special rights at all (i.e. can be just enabled by default in contrast to F_SETFL), but I am not capsicum expert. -- http://ache.vniz.net/ _______________________________________________ firstname.lastname@example.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"