Hello Al, Meanwhile, have you had the opportunity to review our patch? Regards, Alex On 11.01.19 16:42, Alexander Lochmann wrote: > 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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