From: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com> To: "J. Bruce Fields" <bfields@fieldses.org> Cc: vasily.isaenko@oracle.com, hch@infradead.org, linux-nfs@vger.kernel.org, sprabhu@redhat.com, xfs@oss.sgi.com Subject: Re: [PATCH] nfsd: revoking of suid/sgid bits after chown() in a consistent way Date: Thu, 12 Dec 2013 15:44:45 +0400 [thread overview] Message-ID: <52A9A1AD.5090103@oracle.com> (raw) In-Reply-To: <20131212033859.GA5978@fieldses.org> On 12/12/2013 07:38 AM, J. Bruce Fields wrote: > On Wed, Dec 11, 2013 at 03:00:22PM +0400, Stanislav Kholmanskikh wrote: >> >> >> On 12/11/2013 02:16 PM, Stanislav Kholmanskikh wrote: >> [cut off] >>> >>> This patch makes NFS to behave like local file systems. >>> >> [cut off] >> >> This patch allows to run generic/193 without any issues with NFSv3. >> >> With NFSv4 generic/193 fails (but with the other issues, which >> existed even before the patch). >> >> generic/193 expects that suid/sgid bits are cleared after the file >> truncation: >> >> touch file >> chown fsgqa:fsgqa file >> chmod u+s file >> echo 'xyz' > file >> ls -l file >> su fsgqa -c 'echo > file' >> ls -l file >> >> With ext4 (for example), we have expectable results: >> -rwSr--r-- 1 fsgqa fsgqa 4 Dec 11 05:21 file >> -rw-r--r-- 1 fsgqa fsgqa 1 Dec 11 05:22 file >> >> With NFSv3 as well: >> -rwSr--r-- 1 fsgqa fsgqa 4 Dec 11 05:24 file >> -rw-r--r-- 1 fsgqa fsgqa 1 Dec 11 05:25 file >> >> But with NFSv4 the bits are not cleared: >> -rwSr--r-- 1 fsgqa fsgqa 1 Dec 11 05:19 file >> -rwSr--r-- 1 fsgqa fsgqa 1 Dec 11 05:21 file >> >> 'echo > file' issues: >> >> open("file", O_WRONLY|O_CREAT|O_TRUNC, 0666) >> >> Can it be because of design differences between NFSv3 and NFSv4? > > In the v3 case I'd expect the open O_TRUNC to result in a SETATTR rpc, > in the v4 case an OPEN rpc. Both result in a call to nfsd_setattr, > though I only see nfsd_setattr turning off the SUID/SGID bits in the > chown case. Are you sure it isn't the subsequent write that clears > those bits? Actually, in the above test script I occasionally swapped positions of "echo 'xyz' > file" and "chmod u+s file". Of course, chmod should be after the writing. Sorry. But here we are: rm -f file; touch file chown fsgqa:fsgqa file echo 'xyz' > file chmod u+s file ls -l file su fsgqa -c 'echo -n > file' # open(O_TRUNC), close() ls -l file su fsgqa -c 'echo > file' # open(O_TRUNC), write("\n"), close() ls -l file With NFSv3 suid is cleared after write: -rwSr--r-- 1 fsgqa fsgqa 4 Dec 12 05:24 file -rwSr--r-- 1 fsgqa fsgqa 0 Dec 12 05:24 file -rw-r--r-- 1 fsgqa fsgqa 1 Dec 12 05:25 file With NFSv4 suid is not cleared after write("\n"): -rwSr--r-- 1 fsgqa fsgqa 4 Dec 12 05:26 file -rwSr--r-- 1 fsgqa fsgqa 0 Dec 12 05:26 file -rwSr--r-- 1 fsgqa fsgqa 1 Dec 12 05:27 file but if we issue "su fsgqa -c 'echo -n b > file'", we will clear it: -rw-r--r-- 1 fsgqa fsgqa 1 Dec 12 05:28 file So if "file" is a file on NFSv4: -rwSr--r-- 1 fsgqa fsgqa 4 Dec 12 05:26 file and we do: fd = open(file, O_WRONLY); then write(fd, "\n", 1) will not clear suid bit, but write(fd, "b", 1) will do. With ext4 suid is cleared after open(O_TRUNC): -rwSr--r-- 1 fsgqa fsgqa 4 Dec 12 05:29 file -rw-r--r-- 1 fsgqa fsgqa 0 Dec 12 05:29 file -rw-r--r-- 1 fsgqa fsgqa 1 Dec 12 05:30 file Execution of (via 'su fsgqa -c ...'): fd = open("file", O_WRONLY); close(fd); if "file" is on ext4 file system and has suid bit on will not clear suid bit. Execution of (via 'su fsgqa -c ...'): fd = open("file", O_WRONLY); write(fd, "a", 1); close(fd); if "file" is on ext4 file system and has suid bit on will clear suid bit. To conclude: 1. With NFS suid is not cleared after open(O_TRUNC) This may be solved by addition of ATTR_SIZE handling in nfsd_setattr (i.e nfsd_sanitize_attrs). Right? 2. NFSv4 treats "\n" on write() specially. No ideas by the moment. > > But looks to me like nfsd_vfs_write (used in both v3 & v4 cases) clears > suid & guid, so I still don't see it. > > --b. > _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs
WARNING: multiple messages have this Message-ID (diff)
From: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com> To: "J. Bruce Fields" <bfields@fieldses.org> Cc: linux-nfs@vger.kernel.org, vasily.isaenko@oracle.com, hch@infradead.org, xfs@oss.sgi.com, sprabhu@redhat.com Subject: Re: [PATCH] nfsd: revoking of suid/sgid bits after chown() in a consistent way Date: Thu, 12 Dec 2013 15:44:45 +0400 [thread overview] Message-ID: <52A9A1AD.5090103@oracle.com> (raw) In-Reply-To: <20131212033859.GA5978@fieldses.org> On 12/12/2013 07:38 AM, J. Bruce Fields wrote: > On Wed, Dec 11, 2013 at 03:00:22PM +0400, Stanislav Kholmanskikh wrote: >> >> >> On 12/11/2013 02:16 PM, Stanislav Kholmanskikh wrote: >> [cut off] >>> >>> This patch makes NFS to behave like local file systems. >>> >> [cut off] >> >> This patch allows to run generic/193 without any issues with NFSv3. >> >> With NFSv4 generic/193 fails (but with the other issues, which >> existed even before the patch). >> >> generic/193 expects that suid/sgid bits are cleared after the file >> truncation: >> >> touch file >> chown fsgqa:fsgqa file >> chmod u+s file >> echo 'xyz' > file >> ls -l file >> su fsgqa -c 'echo > file' >> ls -l file >> >> With ext4 (for example), we have expectable results: >> -rwSr--r-- 1 fsgqa fsgqa 4 Dec 11 05:21 file >> -rw-r--r-- 1 fsgqa fsgqa 1 Dec 11 05:22 file >> >> With NFSv3 as well: >> -rwSr--r-- 1 fsgqa fsgqa 4 Dec 11 05:24 file >> -rw-r--r-- 1 fsgqa fsgqa 1 Dec 11 05:25 file >> >> But with NFSv4 the bits are not cleared: >> -rwSr--r-- 1 fsgqa fsgqa 1 Dec 11 05:19 file >> -rwSr--r-- 1 fsgqa fsgqa 1 Dec 11 05:21 file >> >> 'echo > file' issues: >> >> open("file", O_WRONLY|O_CREAT|O_TRUNC, 0666) >> >> Can it be because of design differences between NFSv3 and NFSv4? > > In the v3 case I'd expect the open O_TRUNC to result in a SETATTR rpc, > in the v4 case an OPEN rpc. Both result in a call to nfsd_setattr, > though I only see nfsd_setattr turning off the SUID/SGID bits in the > chown case. Are you sure it isn't the subsequent write that clears > those bits? Actually, in the above test script I occasionally swapped positions of "echo 'xyz' > file" and "chmod u+s file". Of course, chmod should be after the writing. Sorry. But here we are: rm -f file; touch file chown fsgqa:fsgqa file echo 'xyz' > file chmod u+s file ls -l file su fsgqa -c 'echo -n > file' # open(O_TRUNC), close() ls -l file su fsgqa -c 'echo > file' # open(O_TRUNC), write("\n"), close() ls -l file With NFSv3 suid is cleared after write: -rwSr--r-- 1 fsgqa fsgqa 4 Dec 12 05:24 file -rwSr--r-- 1 fsgqa fsgqa 0 Dec 12 05:24 file -rw-r--r-- 1 fsgqa fsgqa 1 Dec 12 05:25 file With NFSv4 suid is not cleared after write("\n"): -rwSr--r-- 1 fsgqa fsgqa 4 Dec 12 05:26 file -rwSr--r-- 1 fsgqa fsgqa 0 Dec 12 05:26 file -rwSr--r-- 1 fsgqa fsgqa 1 Dec 12 05:27 file but if we issue "su fsgqa -c 'echo -n b > file'", we will clear it: -rw-r--r-- 1 fsgqa fsgqa 1 Dec 12 05:28 file So if "file" is a file on NFSv4: -rwSr--r-- 1 fsgqa fsgqa 4 Dec 12 05:26 file and we do: fd = open(file, O_WRONLY); then write(fd, "\n", 1) will not clear suid bit, but write(fd, "b", 1) will do. With ext4 suid is cleared after open(O_TRUNC): -rwSr--r-- 1 fsgqa fsgqa 4 Dec 12 05:29 file -rw-r--r-- 1 fsgqa fsgqa 0 Dec 12 05:29 file -rw-r--r-- 1 fsgqa fsgqa 1 Dec 12 05:30 file Execution of (via 'su fsgqa -c ...'): fd = open("file", O_WRONLY); close(fd); if "file" is on ext4 file system and has suid bit on will not clear suid bit. Execution of (via 'su fsgqa -c ...'): fd = open("file", O_WRONLY); write(fd, "a", 1); close(fd); if "file" is on ext4 file system and has suid bit on will clear suid bit. To conclude: 1. With NFS suid is not cleared after open(O_TRUNC) This may be solved by addition of ATTR_SIZE handling in nfsd_setattr (i.e nfsd_sanitize_attrs). Right? 2. NFSv4 treats "\n" on write() specially. No ideas by the moment. > > But looks to me like nfsd_vfs_write (used in both v3 & v4 cases) clears > suid & guid, so I still don't see it. > > --b. >
next prev parent reply other threads:[~2013-12-12 11:45 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-11-06 11:56 nfs vs xfstests 193 Christoph Hellwig 2013-11-06 11:56 ` Christoph Hellwig 2013-12-06 13:20 ` Stanislav Kholmanskikh 2013-12-06 13:20 ` Stanislav Kholmanskikh 2013-12-06 18:08 ` Christoph Hellwig 2013-12-06 18:08 ` Christoph Hellwig 2013-12-06 20:44 ` J. Bruce Fields 2013-12-06 20:44 ` J. Bruce Fields 2013-12-06 20:47 ` J. Bruce Fields 2013-12-06 20:47 ` J. Bruce Fields 2013-12-10 14:43 ` Stanislav Kholmanskikh 2013-12-10 14:43 ` Stanislav Kholmanskikh 2013-12-11 10:16 ` [PATCH] nfsd: revoking of suid/sgid bits after chown() in a consistent way Stanislav Kholmanskikh 2013-12-11 10:16 ` Stanislav Kholmanskikh 2013-12-11 11:00 ` Stanislav Kholmanskikh 2013-12-11 11:00 ` Stanislav Kholmanskikh 2013-12-12 3:38 ` J. Bruce Fields 2013-12-12 3:38 ` J. Bruce Fields 2013-12-12 8:13 ` Christoph Hellwig 2013-12-12 8:13 ` Christoph Hellwig 2013-12-12 11:44 ` Stanislav Kholmanskikh [this message] 2013-12-12 11:44 ` Stanislav Kholmanskikh 2013-12-12 16:01 ` J. Bruce Fields 2013-12-12 16:01 ` J. Bruce Fields
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