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Subject[PATCH 5/6] readdir.c: get compat_filldir() more or less in sync with filldir()
Date
From: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/readdir.c | 51 +++++++++++++++++++++++++++------------------------
1 file changed, 27 insertions(+), 24 deletions(-)

diff --git a/fs/readdir.c b/fs/readdir.c
index a9085016a619..9534675880ce 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -473,7 +473,7 @@ struct compat_linux_dirent {
struct compat_getdents_callback {
struct dir_context ctx;
struct compat_linux_dirent __user *current_dir;
- struct compat_linux_dirent __user *previous;
+ int prev_reclen;
int count;
int error;
};
@@ -481,13 +481,17 @@ struct compat_getdents_callback {
static int compat_filldir(struct dir_context *ctx, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
- struct compat_linux_dirent __user * dirent;
+ struct compat_linux_dirent __user *dirent, *prev;
struct compat_getdents_callback *buf =
container_of(ctx, struct compat_getdents_callback, ctx);
compat_ulong_t d_ino;
int reclen = ALIGN(offsetof(struct compat_linux_dirent, d_name) +
namlen + 2, sizeof(compat_long_t));
+ int prev_reclen;

+ buf->error = verify_dirent_name(name, namlen);
+ if (unlikely(buf->error))
+ return buf->error;
buf->error = -EINVAL; /* only used if we fail.. */
if (reclen > buf->count)
return -EINVAL;
@@ -496,29 +500,27 @@ static int compat_filldir(struct dir_context *ctx, const char *name, int namlen,
buf->error = -EOVERFLOW;
return -EOVERFLOW;
}
- dirent = buf->previous;
- if (dirent) {
- if (signal_pending(current))
- return -EINTR;
- if (__put_user(offset, &dirent->d_off))
- goto efault;
- }
+ prev_reclen = buf->prev_reclen;
+ if (prev_reclen && signal_pending(current))
+ return -EINTR;
dirent = buf->current_dir;
- if (__put_user(d_ino, &dirent->d_ino))
- goto efault;
- if (__put_user(reclen, &dirent->d_reclen))
- goto efault;
- if (copy_to_user(dirent->d_name, name, namlen))
- goto efault;
- if (__put_user(0, dirent->d_name + namlen))
- goto efault;
- if (__put_user(d_type, (char __user *) dirent + reclen - 1))
+ prev = (void __user *) dirent - prev_reclen;
+ if (!user_write_access_begin(prev, reclen + prev_reclen))
goto efault;
- buf->previous = dirent;
- dirent = (void __user *)dirent + reclen;
- buf->current_dir = dirent;
+
+ unsafe_put_user(offset, &prev->d_off, efault_end);
+ unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
+ unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
+ unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
+ unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
+ user_write_access_end();
+
+ buf->prev_reclen = reclen;
+ buf->current_dir = (void __user *)dirent + reclen;
buf->count -= reclen;
return 0;
+efault_end:
+ user_write_access_end();
efault:
buf->error = -EFAULT;
return -EFAULT;
@@ -528,7 +530,6 @@ COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd,
struct compat_linux_dirent __user *, dirent, unsigned int, count)
{
struct fd f;
- struct compat_linux_dirent __user * lastdirent;
struct compat_getdents_callback buf = {
.ctx.actor = compat_filldir,
.current_dir = dirent,
@@ -546,8 +547,10 @@ COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd,
error = iterate_dir(f.file, &buf.ctx);
if (error >= 0)
error = buf.error;
- lastdirent = buf.previous;
- if (lastdirent) {
+ if (buf.prev_reclen) {
+ struct compat_linux_dirent __user * lastdirent;
+ lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;
+
if (put_user(buf.ctx.pos, &lastdirent->d_off))
error = -EFAULT;
else
--
2.11.0
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