From f5beeb1851ea6f8cfcf2657f26cb24c0582b4945 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Thu, 8 Sep 2016 09:57:07 +0200 Subject: fs/proc/kcore.c: Make bounce buffer global for read Next patch adds bounce buffer for ktext area, so it's convenient to have single bounce buffer for both vmalloc/module and ktext cases. Suggested-by: Linus Torvalds Signed-off-by: Jiri Olsa Acked-by: Kees Cook Signed-off-by: Linus Torvalds --- fs/proc/kcore.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) (limited to 'fs/proc') diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index a939f5ed7f89..bd3ac9dca252 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -430,6 +430,7 @@ static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff) static ssize_t read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) { + char *buf = file->private_data; ssize_t acc = 0; size_t size, tsz; size_t elf_buflen; @@ -500,18 +501,10 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) if (clear_user(buffer, tsz)) return -EFAULT; } else if (is_vmalloc_or_module_addr((void *)start)) { - char * elf_buf; - - elf_buf = kzalloc(tsz, GFP_KERNEL); - if (!elf_buf) - return -ENOMEM; - vread(elf_buf, (char *)start, tsz); + vread(buf, (char *)start, tsz); /* we have to zero-fill user buffer even if no read */ - if (copy_to_user(buffer, elf_buf, tsz)) { - kfree(elf_buf); + if (copy_to_user(buffer, buf, tsz)) return -EFAULT; - } - kfree(elf_buf); } else { if (kern_addr_valid(start)) { unsigned long n; @@ -549,6 +542,11 @@ static int open_kcore(struct inode *inode, struct file *filp) { if (!capable(CAP_SYS_RAWIO)) return -EPERM; + + 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) { @@ -559,10 +557,16 @@ 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 file_operations proc_kcore_operations = { .read = read_kcore, .open = open_kcore, + .release = release_kcore, .llseek = default_llseek, }; -- cgit v1.2.3 From df04abfd181acc276ba6762c8206891ae10ae00d Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Thu, 8 Sep 2016 09:57:08 +0200 Subject: fs/proc/kcore.c: Add bounce buffer for ktext data We hit hardened usercopy feature check for kernel text access by reading kcore file: usercopy: kernel memory exposure attempt detected from ffffffff8179a01f () (4065 bytes) kernel BUG at mm/usercopy.c:75! Bypassing this check for kcore by adding bounce buffer for ktext data. Reported-by: Steve Best Fixes: f5509cc18daa ("mm: Hardened usercopy") Suggested-by: Kees Cook Signed-off-by: Jiri Olsa Acked-by: Kees Cook Signed-off-by: Linus Torvalds --- fs/proc/kcore.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'fs/proc') diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index bd3ac9dca252..5c89a07e3d7f 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -509,7 +509,12 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) if (kern_addr_valid(start)) { unsigned long n; - n = copy_to_user(buffer, (char *)start, tsz); + /* + * Using bounce buffer to bypass the + * hardened user copy kernel text checks. + */ + memcpy(buf, (char *) start, tsz); + n = copy_to_user(buffer, buf, tsz); /* * We cannot distinguish between fault on source * and fault on destination. When this happens -- cgit v1.2.3