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charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 02, 2023 at 12:01:16AM +0800, Baoquan He wrote: > On 08/01/23 at 11:57pm, Baoquan He wrote: > > On 07/31/23 at 10:50pm, Lorenzo Stoakes wrote: > > > Some architectures do not populate the entire range categorised by > > > KCORE_TEXT, so we must ensure that the kernel address we read from is > > > valid. > > > > > > Unfortunately there is no solution currently available to do so with a > > > purely iterator solution so reinstate the bounce buffer in this instance so > > > we can use copy_from_kernel_nofault() in order to avoid page faults when > > > regions are unmapped. > > > > > > This change partly reverts commit 2e1c0170771e ("fs/proc/kcore: avoid > > > bounce buffer for ktext data"), reinstating the bounce buffer, but adapts > > > the code to continue to use an iterator. > > > > > > Fixes: 2e1c0170771e ("fs/proc/kcore: avoid bounce buffer for ktext data") > > > Reported-by: Jiri Olsa > > > Closes: https://lore.kernel.org/all/ZHc2fm+9daF6cgCE@krava > > > Cc: stable@vger.kernel.org > > > Signed-off-by: Lorenzo Stoakes > > > --- > > > fs/proc/kcore.c | 26 +++++++++++++++++++++++++- > > > 1 file changed, 25 insertions(+), 1 deletion(-) > > > > > > diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c > > > index 9cb32e1a78a0..3bc689038232 100644 > > > --- a/fs/proc/kcore.c > > > +++ b/fs/proc/kcore.c > > > @@ -309,6 +309,8 @@ static void append_kcore_note(char *notes, size_t *i, const char *name, > > > > > > static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter) > > > { > > > + struct file *file = iocb->ki_filp; > > > + char *buf = file->private_data; > > > loff_t *fpos = &iocb->ki_pos; > > > size_t phdrs_offset, notes_offset, data_offset; > > > size_t page_offline_frozen = 1; > > > @@ -554,11 +556,22 @@ static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter) > > > fallthrough; > > > case KCORE_VMEMMAP: > > > case KCORE_TEXT: > > > + /* > > > + * Sadly we must use a bounce buffer here to be able to > > > + * make use of copy_from_kernel_nofault(), as these > > > + * memory regions might not always be mapped on all > > > + * architectures. > > > + */ > > > + if (copy_from_kernel_nofault(buf, (void *)start, tsz)) { > > > + if (iov_iter_zero(tsz, iter) != tsz) { > > > + ret = -EFAULT; > > > + goto out; > > > + } > > > /* > > > * We use _copy_to_iter() to bypass usermode hardening > > > * which would otherwise prevent this operation. > > > */ > > > - if (_copy_to_iter((char *)start, tsz, iter) != tsz) { > > > + } else if (_copy_to_iter(buf, tsz, iter) != tsz) { > > > ret = -EFAULT; > > > goto out; > > > } > > > @@ -595,6 +608,10 @@ static int open_kcore(struct inode *inode, struct file *filp) > > > if (ret) > > > return ret; > > > > > > + filp->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL); > > > + if (!filp->private_data) > > > + return -ENOMEM; > > > + > > > if (kcore_need_update) > > > kcore_update_ram(); > > > if (i_size_read(inode) != proc_root_kcore->size) { > > > @@ -605,9 +622,16 @@ static int open_kcore(struct inode *inode, struct file *filp) > > > return 0; > > > } > > > > > > +static int release_kcore(struct inode *inode, struct file *file) > > > +{ > > > + kfree(file->private_data); > > > + return 0; > > > +} > > > + > > > static const struct proc_ops kcore_proc_ops = { > > > .proc_read_iter = read_kcore_iter, > > > .proc_open = open_kcore, > > > + .proc_release = release_kcore, > > > .proc_lseek = default_llseek, > > > }; > > > > On 6.5-rc4, the failures can be reproduced stably on a arm64 machine. > > With patch applied, both makedumpfile and objdump test cases passed. > > > > And the code change looks good to me, thanks. > > > > Tested-by: Baoquan He > > Reviewed-by: Baoquan He Thanks! > > > > > > =============================================== > > [root@ ~]# makedumpfile --mem-usage /proc/kcore > > The kernel version is not supported. > > The makedumpfile operation may be incomplete. > > > > TYPE PAGES EXCLUDABLE DESCRIPTION > > ---------------------------------------------------------------------- > > ZERO 76234 yes Pages filled with zero > > NON_PRI_CACHE 147613 yes Cache pages without private flag > > PRI_CACHE 3847 yes Cache pages with private flag > > USER 15276 yes User process pages > > FREE 15809884 yes Free pages > > KERN_DATA 459950 no Dumpable kernel data > > > > page size: 4096 > > Total pages on system: 16512804 > > Total size on system: 67636445184 Byte > > > > [root@ ~]# objdump -d --start-address=0x^C > > [root@ ~]# cat /proc/kallsyms | grep ksys_read > > ffffab3be77229d8 T ksys_readahead > > ffffab3be782a700 T ksys_read > > [root@ ~]# objdump -d --start-address=0xffffab3be782a700 --stop-address=0xffffab3be782a710 /proc/kcore > > > > /proc/kcore: file format elf64-littleaarch64 > > > > > > Disassembly of section load1: > > > > ffffab3be782a700 : > > ffffab3be782a700: aa1e03e9 mov x9, x30 > > ffffab3be782a704: d503201f nop > > ffffab3be782a708: d503233f paciasp > > ffffab3be782a70c: a9bc7bfd stp x29, x30, [sp, #-64]! > > objdump: error: /proc/kcore(load2) is too large (0x7bff70000000 bytes) > > objdump: Reading section load2 failed because: memory exhausted > > By the way, I can still see the objdump error saying kcore is too large > as above, at the same time there's console printing as below. Haven't > checked it's objdump's issue or kernel's. > > [ 6631.575800] __vm_enough_memory: pid: 5321, comm: objdump, not enough memory for the allocation > [ 6631.584469] __vm_enough_memory: pid: 5321, comm: objdump, not enough memory for the allocation > Yeah this issue existed before this patch was applied on arm64, apparently an ancient objdump bug according to the other thread [0]. I confirmed it exists on v6.0 kernel for instance. [0]:https://lore.kernel.org/all/7b94619ad89c9e308c7aedef2cacfa10b8666e69.camel@gmx.de/