Hello Al, Have you had the opportunity to review our patch? Cheers, Alex On 17.12.18 09:28, Jan Kara wrote: > On Fri 14-12-18 11:55:52, Alexander Lochmann wrote: >> >> file_remove_privs() might be called for non-regular files, e.g. >> blkdev inode. There is no reason to do its job on things >> like blkdev inodes, pipes, or cdevs. Hence, abort if >> file does not refer to a regular inode. >> The following stacktrace shows how to get there: >> 13: entry_SYSENTER_32:460 >> 12: do_fast_syscall_32:410 >> 11: _static_cpu_has:146 >> 10: do_syscall_32_irqs_on:322 >> 09: SyS_pwrite64:636 >> 08: SYSC_pwrite64:650 >> 07: fdput:38 >> 06: vfs_write:560 >> 05: __vfs_write:512 >> 04: new_sync_write:500 >> 03: blkdev_write_iter:1977 >> 02: __generic_file_write_iter:2897 >> 01: file_remove_privs:1818 >> 00: inode_has_no_xattr:3163 >> >> Found by LockDoc (Alexander Lochmann, Horst Schirmeier and Olaf >> Spinczyk) >> >> Signed-off-by: Alexander Lochmann <alexander.lochmann@xxxxxxxxxxxxxx> >> Signed-off-by: Horst Schirmeier <horst.schirmeier@xxxxxxxxxxxxxx> > > The patch looks good to me. You can add: > > Reviewed-by: Jan Kara <jack@xxxxxxx> > > Honza > >> --- >> fs/inode.c | 9 +++++++-- >> 1 file changed, 7 insertions(+), 2 deletions(-) >> >> diff --git a/fs/inode.c b/fs/inode.c >> index 35d2108d567c..682088190413 100644 >> --- a/fs/inode.c >> +++ b/fs/inode.c >> @@ -1820,8 +1820,13 @@ int file_remove_privs(struct file *file) >> int kill; >> int error = 0; >> >> - /* Fast path for nothing security related */ >> - if (IS_NOSEC(inode)) >> + /* >> + * Fast path for nothing security related. >> + * As well for non-regular files, e.g. blkdev inodes. >> + * For example, blkdev_write_iter() might get here >> + * trying to remove privs which it is not allowed to. >> + */ >> + if (IS_NOSEC(inode) || !S_ISREG(inode->i_mode)) >> return 0; >> >> kill = dentry_needs_remove_privs(dentry); >> -- >> 2.19.2 >> > > > -- Technische Universität Dortmund Alexander Lochmann PGP key: 0xBC3EF6FD Otto-Hahn-Str. 16 phone: +49.231.7556141 D-44227 Dortmund fax: +49.231.7556116 http://ess.cs.tu-dortmund.de/Staff/al
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