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proc/kcore: hold lock during read

Browse source 
Now that we're using an rwsem, we can hold it during the entirety of
read_kcore() and have a common return path.  This is preparation for the
next change.

[[email protected]: fix locking bug reported by Tetsuo Handa]
Link: http://lkml.kernel.org/r/d7cfbc1e8a76616f3b699eaff9df0a2730380534.1531953780.git.osandov@fb.com
Signed-off-by: Omar Sandoval <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Bhupesh Sharma <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: James Morse <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Omar Sandoval 2018-08-21 21:55:06 -07:00 • committed by Linus Torvalds
commit 3673fb08db
1 changed files with 40 additions and 30 deletions
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70
fs/proc/kcore.c
View file

@ -440,19 +440,18 @@ 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;
int nphdr;
unsigned long start;
size_t orig_buflen = buflen;
int ret = 0;
down_read(&kclist_lock);
size = get_kcore_size(&nphdr, &elf_buflen);
if (buflen == 0 || *fpos >= size) {
up_read(&kclist_lock);
return 0;
}
if (buflen == 0 || *fpos >= size)
goto out;
/* trim buflen to not go beyond EOF */
if (buflen > size - *fpos)
@ -465,28 +464,26 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
tsz = elf_buflen - *fpos;
if (buflen < tsz)
tsz = buflen;
elf_buf = kzalloc(elf_buflen, GFP_ATOMIC);
elf_buf = kzalloc(elf_buflen, GFP_KERNEL);
if (!elf_buf) {
up_read(&kclist_lock);
return -ENOMEM;
ret = -ENOMEM;
goto out;
}
elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen);
up_read(&kclist_lock);
if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
kfree(elf_buf);
return -EFAULT;
ret = -EFAULT;
goto out;
}
kfree(elf_buf);
buflen -= tsz;
*fpos += tsz;
buffer += tsz;
acc += tsz;
/* leave now if filled buffer already */
if (buflen == 0)
return acc;
} else
up_read(&kclist_lock);
goto out;
}
/*
* Check to see if our file offset matches with any of
@ -499,25 +496,29 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
while (buflen) {
struct kcore_list *m;
down_read(&kclist_lock);
list_for_each_entry(m, &kclist_head, list) {
if (start >= m->addr && start < (m->addr+m->size))
break;
}
up_read(&kclist_lock);
if (&m->list == &kclist_head) {
if (clear_user(buffer, tsz))
return -EFAULT;
if (clear_user(buffer, tsz)) {
ret = -EFAULT;
goto out;
}
} else if (m->type == KCORE_VMALLOC) {
vread(buf, (char *)start, tsz);
/* we have to zero-fill user buffer even if no read */
if (copy_to_user(buffer, buf, tsz))
return -EFAULT;
if (copy_to_user(buffer, buf, tsz)) {
ret = -EFAULT;
goto out;
}
} else if (m->type == KCORE_USER) {
/* User page is handled prior to normal kernel page: */
if (copy_to_user(buffer, (char *)start, tsz))
return -EFAULT;
if (copy_to_user(buffer, (char *)start, tsz)) {
ret = -EFAULT;
goto out;
}
} else {
if (kern_addr_valid(start)) {
/*
@ -525,26 +526,35 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
* hardened user copy kernel text checks.
*/
if (probe_kernel_read(buf, (void *) start, tsz)) {
if (clear_user(buffer, tsz))
return -EFAULT;
if (clear_user(buffer, tsz)) {
ret = -EFAULT;
goto out;
}
} else {
if (copy_to_user(buffer, buf, tsz))
return -EFAULT;
if (copy_to_user(buffer, buf, tsz)) {
ret = -EFAULT;
goto out;
}
}
} else {
if (clear_user(buffer, tsz))
return -EFAULT;
if (clear_user(buffer, tsz)) {
ret = -EFAULT;
goto out;
}
}
}
buflen -= tsz;
*fpos += tsz;
buffer += tsz;
acc += tsz;
start += tsz;
tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
}
return acc;
out:
up_read(&kclist_lock);
if (ret)
return ret;
return orig_buflen - buflen;
}