From: Lorenzo Stoakes lstoakes@gmail.com
commit 17457784004c84178798432a029ab20e14f728b1 upstream.
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.
[lstoakes@gmail.com: correct comment to be strictly correct about reasoning] Link: https://lkml.kernel.org/r/525a3f14-74fa-4c22-9fca-9dab4de8a0c3@lucifer.local Link: https://lkml.kernel.org/r/20230731215021.70911-1-lstoakes@gmail.com Fixes: 2e1c0170771e ("fs/proc/kcore: avoid bounce buffer for ktext data") Signed-off-by: Lorenzo Stoakes lstoakes@gmail.com Reported-by: Jiri Olsa olsajiri@gmail.com Closes: https://lore.kernel.org/all/ZHc2fm+9daF6cgCE@krava Tested-by: Jiri Olsa jolsa@kernel.org Tested-by: Will Deacon will@kernel.org Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: Ard Biesheuvel ardb@kernel.org Cc: Baoquan He bhe@redhat.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: David Hildenbrand david@redhat.com Cc: Jens Axboe axboe@kernel.dk Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: Liu Shixin liushixin2@huawei.com Cc: Matthew Wilcox willy@infradead.org Cc: Mike Galbraith efault@gmx.de Cc: Thorsten Leemhuis regressions@leemhuis.info Cc: Uladzislau Rezki (Sony) urezki@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/proc/kcore.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-)
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 9cb32e1a78a0..23fc24d16b31 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; @@ -555,10 +557,21 @@ static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter) case KCORE_VMEMMAP: case KCORE_TEXT: /* - * We use _copy_to_iter() to bypass usermode hardening - * which would otherwise prevent this operation. + * 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_to_iter((char *)start, tsz, iter) != tsz) { + if (copy_from_kernel_nofault(buf, (void *)start, tsz)) { + if (iov_iter_zero(tsz, iter) != tsz) { + ret = -EFAULT; + goto out; + } + /* + * We know the bounce buffer is safe to copy from, so + * use _copy_to_iter() directly. + */ + } 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, };