6.1-stable review patch. If anyone has any objections, please let me know.
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From: Lorenzo Stoakes lstoakes@gmail.com
[ Upstream commit 2e1c0170771e6bf31bc785ea43a44e6e85e36268 ]
Patch series "convert read_kcore(), vread() to use iterators", v8.
While reviewing Baoquan's recent changes to permit vread() access to vm_map_ram regions of vmalloc allocations, Willy pointed out [1] that it would be nice to refactor vread() as a whole, since its only user is read_kcore() and the existing form of vread() necessitates the use of a bounce buffer.
This patch series does exactly that, as well as adjusting how we read the kernel text section to avoid the use of a bounce buffer in this case as well.
This has been tested against the test case which motivated Baoquan's changes in the first place [2] which continues to function correctly, as do the vmalloc self tests.
This patch (of 4):
Commit df04abfd181a ("fs/proc/kcore.c: Add bounce buffer for ktext data") introduced the use of a bounce buffer to retrieve kernel text data for /proc/kcore in order to avoid failures arising from hardened user copies enabled by CONFIG_HARDENED_USERCOPY in check_kernel_text_object().
We can avoid doing this if instead of copy_to_user() we use _copy_to_user() which bypasses the hardening check. This is more efficient than using a bounce buffer and simplifies the code.
We do so as part an overall effort to eliminate bounce buffer usage in the function with an eye to converting it an iterator read.
Link: https://lkml.kernel.org/r/cover.1679566220.git.lstoakes@gmail.com Link: https://lore.kernel.org/all/Y8WfDSRkc%2FOHP3oD@casper.infradead.org/ [1] Link: https://lore.kernel.org/all/87ilk6gos2.fsf@oracle.com/T/#u [2] Link: https://lkml.kernel.org/r/fd39b0bfa7edc76d360def7d034baaee71d90158.167951114... Signed-off-by: Lorenzo Stoakes lstoakes@gmail.com Reviewed-by: David Hildenbrand david@redhat.com Reviewed-by: Baoquan He bhe@redhat.com Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: Jens Axboe axboe@kernel.dk Cc: Jiri Olsa jolsa@kernel.org Cc: Liu Shixin liushixin2@huawei.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Uladzislau Rezki (Sony) urezki@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Stable-dep-of: 3d5854d75e31 ("fs/proc/kcore.c: allow translation of physical memory addresses") Signed-off-by: Sasha Levin sashal@kernel.org --- fs/proc/kcore.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-)
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 590ecb79ad8b6..786e5e90f670c 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -542,19 +542,12 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) case KCORE_VMEMMAP: case KCORE_TEXT: /* - * Using bounce buffer to bypass the - * hardened user copy kernel text checks. + * We use _copy_to_user() to bypass usermode hardening + * which would otherwise prevent this operation. */ - if (copy_from_kernel_nofault(buf, (void *)start, tsz)) { - if (clear_user(buffer, tsz)) { - ret = -EFAULT; - goto out; - } - } else { - if (copy_to_user(buffer, buf, tsz)) { - ret = -EFAULT; - goto out; - } + if (_copy_to_user(buffer, (char *)start, tsz)) { + ret = -EFAULT; + goto out; } break; default: