From: Al Viro viro@zeniv.linux.org.uk
[ Upstream commit 06bbaa6dc53cb72040db952053432541acb9adc7 ]
passing kmap_local_page() result to __kernel_write() is unsafe - random ->write_iter() might (and 9p one does) get unhappy when passed ITER_KVEC with pointer that came from kmap_local_page().
Fix by providing a variant of __kernel_write() that takes an iov_iter from caller (__kernel_write() becomes a trivial wrapper) and adding dump_emit_page() that parallels dump_emit(), except that instead of __kernel_write() it uses __kernel_write_iter() with ITER_BVEC source.
Fixes: 3159ed57792b "fs/coredump: use kmap_local_page()" Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/coredump.c | 38 +++++++++++++++++++++++++++++++++----- fs/internal.h | 3 +++ fs/read_write.c | 22 ++++++++++++++-------- 3 files changed, 50 insertions(+), 13 deletions(-)
diff --git a/fs/coredump.c b/fs/coredump.c index 26eb5a095832..43fdd82f82ab 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -902,6 +902,38 @@ static int __dump_skip(struct coredump_params *cprm, size_t nr) } }
+static int dump_emit_page(struct coredump_params *cprm, struct page *page) +{ + struct bio_vec bvec = { + .bv_page = page, + .bv_offset = 0, + .bv_len = PAGE_SIZE, + }; + struct iov_iter iter; + struct file *file = cprm->file; + loff_t pos = file->f_pos; + ssize_t n; + + if (cprm->to_skip) { + if (!__dump_skip(cprm, cprm->to_skip)) + return 0; + cprm->to_skip = 0; + } + if (cprm->written + PAGE_SIZE > cprm->limit) + return 0; + if (dump_interrupted()) + return 0; + iov_iter_bvec(&iter, WRITE, &bvec, 1, PAGE_SIZE); + n = __kernel_write_iter(cprm->file, &iter, &pos); + if (n != PAGE_SIZE) + return 0; + file->f_pos = pos; + cprm->written += PAGE_SIZE; + cprm->pos += PAGE_SIZE; + + return 1; +} + int dump_emit(struct coredump_params *cprm, const void *addr, int nr) { if (cprm->to_skip) { @@ -933,7 +965,6 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
for (addr = start; addr < start + len; addr += PAGE_SIZE) { struct page *page; - int stop;
/* * To avoid having to allocate page tables for virtual address @@ -944,10 +975,7 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start, */ page = get_dump_page(addr); if (page) { - void *kaddr = kmap_local_page(page); - - stop = !dump_emit(cprm, kaddr, PAGE_SIZE); - kunmap_local(kaddr); + int stop = !dump_emit_page(cprm, page); put_page(page); if (stop) return 0; diff --git a/fs/internal.h b/fs/internal.h index 4f1fe6d08866..69b64136ae4c 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -16,6 +16,7 @@ struct shrink_control; struct fs_context; struct user_namespace; struct pipe_inode_info; +struct iov_iter;
/* * block/bdev.c @@ -219,3 +220,5 @@ struct xattr_ctx { int setxattr_copy(const char __user *name, struct xattr_ctx *ctx); int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry, struct xattr_ctx *ctx); + +ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos); diff --git a/fs/read_write.c b/fs/read_write.c index 8d3ec975514d..08299a8f3e05 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -512,14 +512,9 @@ static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t }
/* caller is responsible for file_start_write/file_end_write */ -ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos) +ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos) { - struct kvec iov = { - .iov_base = (void *)buf, - .iov_len = min_t(size_t, count, MAX_RW_COUNT), - }; struct kiocb kiocb; - struct iov_iter iter; ssize_t ret;
if (WARN_ON_ONCE(!(file->f_mode & FMODE_WRITE))) @@ -535,8 +530,7 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
init_sync_kiocb(&kiocb, file); kiocb.ki_pos = pos ? *pos : 0; - iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len); - ret = file->f_op->write_iter(&kiocb, &iter); + ret = file->f_op->write_iter(&kiocb, from); if (ret > 0) { if (pos) *pos = kiocb.ki_pos; @@ -546,6 +540,18 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t inc_syscw(current); return ret; } + +/* caller is responsible for file_start_write/file_end_write */ +ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos) +{ + struct kvec iov = { + .iov_base = (void *)buf, + .iov_len = min_t(size_t, count, MAX_RW_COUNT), + }; + struct iov_iter iter; + iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len); + return __kernel_write_iter(file, &iter, pos); +} /* * This "EXPORT_SYMBOL_GPL()" is more of a "EXPORT_SYMBOL_DONTUSE()", * but autofs is one of the few internal kernel users that actually