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    SubjectRe: [PATCH v2 1/6] fs/readdir: Fix filldir() and filldir64() use of user_access_begin()
    Date
    Hi Christophe,

    This patch is independent of the rest of the series AFAICS, and it looks
    like Linus has modified it quite a bit down thread.

    So I'll take patches 2-6 via powerpc and assume this patch will go via
    Linus or Al or elsewhere.

    Also a couple of minor spelling fixes below.

    cheers

    Christophe Leroy <christophe.leroy@c-s.fr> writes:
    > Some architectures grand full access to userspace regardless of the
    ^
    grant
    > address/len passed to user_access_begin(), but other architectures
    > only grand access to the requested area.
    ^
    grant
    >
    > For exemple, on 32 bits powerpc (book3s/32), access is granted by
    ^
    example
    > segments of 256 Mbytes.
    >
    > Modify filldir() and filldir64() to request the real area they need
    > to get access to, i.e. the area covering the parent dirent (if any)
    > and the contiguous current dirent.
    >
    > Fixes: 9f79b78ef744 ("Convert filldir[64]() from __put_user() to unsafe_put_user()")
    > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
    > ---
    > v2: have user_access_begin() cover both parent dirent (if any) and current dirent
    > ---
    > fs/readdir.c | 50 ++++++++++++++++++++++++++++----------------------
    > 1 file changed, 28 insertions(+), 22 deletions(-)
    >
    > diff --git a/fs/readdir.c b/fs/readdir.c
    > index d26d5ea4de7b..3f9b4488d9b7 100644
    > --- a/fs/readdir.c
    > +++ b/fs/readdir.c
    > @@ -214,7 +214,7 @@ struct getdents_callback {
    > static int filldir(struct dir_context *ctx, const char *name, int namlen,
    > loff_t offset, u64 ino, unsigned int d_type)
    > {
    > - struct linux_dirent __user * dirent;
    > + struct linux_dirent __user * dirent, *dirent0;
    > struct getdents_callback *buf =
    > container_of(ctx, struct getdents_callback, ctx);
    > unsigned long d_ino;
    > @@ -232,19 +232,22 @@ static int filldir(struct dir_context *ctx, const char *name, int namlen,
    > buf->error = -EOVERFLOW;
    > return -EOVERFLOW;
    > }
    > - dirent = buf->previous;
    > - if (dirent && signal_pending(current))
    > + dirent0 = buf->previous;
    > + if (dirent0 && signal_pending(current))
    > return -EINTR;
    >
    > - /*
    > - * Note! This range-checks 'previous' (which may be NULL).
    > - * The real range was checked in getdents
    > - */
    > - if (!user_access_begin(dirent, sizeof(*dirent)))
    > - goto efault;
    > - if (dirent)
    > - unsafe_put_user(offset, &dirent->d_off, efault_end);
    > dirent = buf->current_dir;
    > + if (dirent0) {
    > + int sz = (void __user *)dirent + reclen -
    > + (void __user *)dirent0;
    > +
    > + if (!user_access_begin(dirent0, sz))
    > + goto efault;
    > + unsafe_put_user(offset, &dirent0->d_off, efault_end);
    > + } else {
    > + if (!user_access_begin(dirent, reclen))
    > + goto efault;
    > + }
    > 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);
    > @@ -307,7 +310,7 @@ struct getdents_callback64 {
    > static int filldir64(struct dir_context *ctx, const char *name, int namlen,
    > loff_t offset, u64 ino, unsigned int d_type)
    > {
    > - struct linux_dirent64 __user *dirent;
    > + struct linux_dirent64 __user *dirent, *dirent0;
    > struct getdents_callback64 *buf =
    > container_of(ctx, struct getdents_callback64, ctx);
    > int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
    > @@ -319,19 +322,22 @@ static int filldir64(struct dir_context *ctx, const char *name, int namlen,
    > buf->error = -EINVAL; /* only used if we fail.. */
    > if (reclen > buf->count)
    > return -EINVAL;
    > - dirent = buf->previous;
    > - if (dirent && signal_pending(current))
    > + dirent0 = buf->previous;
    > + if (dirent0 && signal_pending(current))
    > return -EINTR;
    >
    > - /*
    > - * Note! This range-checks 'previous' (which may be NULL).
    > - * The real range was checked in getdents
    > - */
    > - if (!user_access_begin(dirent, sizeof(*dirent)))
    > - goto efault;
    > - if (dirent)
    > - unsafe_put_user(offset, &dirent->d_off, efault_end);
    > dirent = buf->current_dir;
    > + if (dirent0) {
    > + int sz = (void __user *)dirent + reclen -
    > + (void __user *)dirent0;
    > +
    > + if (!user_access_begin(dirent0, sz))
    > + goto efault;
    > + unsafe_put_user(offset, &dirent0->d_off, efault_end);
    > + } else {
    > + if (!user_access_begin(dirent, reclen))
    > + goto efault;
    > + }
    > unsafe_put_user(ino, &dirent->d_ino, efault_end);
    > unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
    > unsafe_put_user(d_type, &dirent->d_type, efault_end);
    > --
    > 2.25.0

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