On 1/30/20 3:26 AM, Christian Brauner wrote: > On Thu, Jan 30, 2020 at 11:11:58AM +0100, Jann Horn wrote: >> On Thu, Jan 30, 2020 at 2:08 AM Jens Axboe <axboe@xxxxxxxxx> wrote: >>> On 1/29/20 10:34 AM, Jens Axboe wrote: >>>> On 1/29/20 7:59 AM, Jann Horn wrote: >>>>> On Tue, Jan 28, 2020 at 8:42 PM Jens Axboe <axboe@xxxxxxxxx> wrote: >>>>>> On 1/28/20 11:04 AM, Jens Axboe wrote: >>>>>>> On 1/28/20 10:19 AM, Jens Axboe wrote: >>>>> [...] >>>>>>>> #1 adds support for registering the personality of the invoking task, >>>>>>>> and #2 adds support for IORING_OP_USE_CREDS. Right now it's limited to >>>>>>>> just having one link, it doesn't support a chain of them. >>>>> [...] >>>>>> I didn't like it becoming a bit too complicated, both in terms of >>>>>> implementation and use. And the fact that we'd have to jump through >>>>>> hoops to make this work for a full chain. >>>>>> >>>>>> So I punted and just added sqe->personality and IOSQE_PERSONALITY. >>>>>> This makes it way easier to use. Same branch: >>>>>> >>>>>> https://git.kernel.dk/cgit/linux-block/log/?h=for-5.6/io_uring-vfs-creds >>>>>> >>>>>> I'd feel much better with this variant for 5.6. >>>>> >>>>> Some general feedback from an inspectability/debuggability perspective: >>>>> >>>>> At some point, it might be nice if you could add a .show_fdinfo >>>>> handler to the io_uring_fops that makes it possible to get a rough >>>>> overview over the state of the uring by reading /proc/$pid/fdinfo/$fd, >>>>> just like e.g. eventfd (see eventfd_show_fdinfo()). It might be >>>>> helpful for debugging to be able to see information about the fixed >>>>> files and buffers that have been registered. Same for the >>>>> personalities; that information might also be useful when someone is >>>>> trying to figure out what privileges a running process actually has. >>>> >>>> Agree, that would be a very useful addition. I'll take a look at it. >>> >>> Jann, how much info are you looking for? Here's a rough start, just >>> shows the number of registered files and buffers, and lists the >>> personalities registered. We could also dump the buffer info for >>> each of them, and ditto for the files. Not sure how much verbosity >>> is acceptable in fdinfo? >> >> At the moment, I personally am just interested in this from the >> perspective of being able to audit the state of personalities, to make >> important information about the security state of processes visible. >> >> Good point about verbosity in fdinfo - I'm not sure about that myself either. >> >>> Here's the test app for personality: >> >> Oh, that was quick... >> >>> # cat 3 >>> pos: 0 >>> flags: 02000002 >>> mnt_id: 14 >>> user-files: 0 >>> user-bufs: 0 >>> personalities: >>> 1: uid=0/gid=0 >>> >>> >>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>> index c5ca84a305d3..0b2c7d800297 100644 >>> --- a/fs/io_uring.c >>> +++ b/fs/io_uring.c >>> @@ -6511,6 +6505,45 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, >>> return submitted ? submitted : ret; >>> } >>> >>> +struct ring_show_idr { >>> + struct io_ring_ctx *ctx; >>> + struct seq_file *m; >>> +}; >>> + >>> +static int io_uring_show_cred(int id, void *p, void *data) >>> +{ >>> + struct ring_show_idr *r = data; >>> + const struct cred *cred = p; >>> + >>> + seq_printf(r->m, "\t%5d: uid=%u/gid=%u\n", id, cred->uid.val, >>> + cred->gid.val); >> >> As Stefan said, the ->uid and ->gid aren't very useful, since when a >> process switches UIDs for accessing things in the filesystem, it >> probably only changes its EUID and FSUID, not its RUID. >> I think what's particularly relevant for uring would be the ->fsuid >> and the ->fsgid along with ->cap_effective; and perhaps for some >> operations also the ->euid and ->egid. The real UID/GID aren't really >> relevant when performing normal filesystem operations and such. > > This should probably just use the same format that is found in > /proc/<pid>/status to make it easy for tools to use the same parsing > logic and for the sake of consistency. We've adapted the same format for > pidfds. So that would mean: > > Uid: 1000 1000 1000 1000 > Gid: 1000 1000 1000 1000 > > Which would be: Real, effective, saved set, and filesystem {G,U}IDs > > And CapEff in /proc/<pid>/status has the format: > CapEff: 0000000000000000 I agree, consistency is good. I've added this, and also changed the naming to be CamelCase, which is seems like most of them are. Now it looks like this: pos: 0 flags: 02000002 mnt_id: 14 UserFiles: 0 UserBufs: 0 Personalities: 1 Uid: 0 0 0 0 Gid: 0 0 0 0 Groups: 0 CapEff: 0000003fffffffff for a single personality registered (root). I have to indent it an extra tab to display each personality. diff --git a/fs/io_uring.c b/fs/io_uring.c index c5ca84a305d3..8b2411542f3e 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -6511,6 +6505,79 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, return submitted ? submitted : ret; } +static int io_uring_show_cred(int id, void *p, void *data) +{ + const struct cred *cred = p; + struct seq_file *m = data; + struct user_namespace *uns = seq_user_ns(m); + struct group_info *gi; + kernel_cap_t cap; + unsigned __capi; + int g; + + seq_printf(m, "%5d\n", id); + seq_put_decimal_ull(m, "\tUid:\t", from_kuid_munged(uns, cred->uid)); + seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->euid)); + seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->suid)); + seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->fsuid)); + seq_put_decimal_ull(m, "\n\tGid:\t", from_kgid_munged(uns, cred->gid)); + seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->egid)); + seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->sgid)); + seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->fsgid)); + seq_puts(m, "\n\tGroups:\t"); + gi = cred->group_info; + for (g = 0; g < gi->ngroups; g++) { + seq_put_decimal_ull(m, g ? " " : "", + from_kgid_munged(uns, gi->gid[g])); + } + seq_puts(m, "\n\tCapEff:\t"); + cap = cred->cap_effective; + CAP_FOR_EACH_U32(__capi) + seq_put_hex_ll(m, NULL, cap.cap[CAP_LAST_U32 - __capi], 8); + seq_putc(m, '\n'); + return 0; +} + +static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m) +{ + int i; + + mutex_lock(&ctx->uring_lock); + seq_printf(m, "UserFiles: %5u\n", ctx->nr_user_files); + for (i = 0; i < ctx->nr_user_files; i++) { + struct fixed_file_table *table; + struct file *f; + + table = &ctx->file_data->table[i >> IORING_FILE_TABLE_SHIFT]; + f = table->files[i & IORING_FILE_TABLE_MASK]; + if (f) + seq_printf(m, "%5u: %s\n", i, file_dentry(f)->d_iname); + else + seq_printf(m, "%5u: <none>\n", i); + } + seq_printf(m, "UserBufs: %5u\n", ctx->nr_user_bufs); + for (i = 0; i < ctx->nr_user_bufs; i++) { + struct io_mapped_ubuf *buf = &ctx->user_bufs[i]; + + seq_printf(m, "%5u: 0x%llx/%lu\n", i, buf->ubuf, buf->len); + } + if (!idr_is_empty(&ctx->personality_idr)) { + seq_printf(m, "Personalities:\n"); + idr_for_each(&ctx->personality_idr, io_uring_show_cred, m); + } + mutex_unlock(&ctx->uring_lock); +} + +static void io_uring_show_fdinfo(struct seq_file *m, struct file *f) +{ + struct io_ring_ctx *ctx = f->private_data; + + if (percpu_ref_tryget(&ctx->refs)) { + __io_uring_show_fdinfo(ctx, m); + percpu_ref_put(&ctx->refs); + } +} + static const struct file_operations io_uring_fops = { .release = io_uring_release, .flush = io_uring_flush, @@ -6521,6 +6588,7 @@ static const struct file_operations io_uring_fops = { #endif .poll = io_uring_poll, .fasync = io_uring_fasync, + .show_fdinfo = io_uring_show_fdinfo, }; static int io_allocate_scq_urings(struct io_ring_ctx *ctx, -- Jens Axboe
