On Wed, Apr 10, 2019 at 09:47:01PM -0500, Steve French wrote:
How was this discovered? Does it address a reported user problem?
I have spotted it while tracking down how page reference are taken for bio and how they are release. In the current code, once the page are GUPed they are never release if there is any failure, on failure cifs_aio_ctx_release() will be call but it will just free the bio_vec not release the page reference.
Page reference are only drop if everything is successful.
So this patch move the page reference droping to cifs_aio_ctx_release() which is call from all code path including failure AFAICT and thus page reference will be drop if failure does happen.
Cheers, Jérôme
On Wed, Apr 10, 2019 at 2:38 PM jglisse@redhat.com wrote:
From: Jérôme Glisse jglisse@redhat.com
CIFS can leak pages reference gotten through GUP (get_user_pages*() through iov_iter_get_pages()). This happen if cifs_send_async_read() or cifs_write_from_iter() calls fail from within __cifs_readv() and __cifs_writev() respectively. This patch move page unreference to cifs_aio_ctx_release() which will happens on all code paths this is all simpler to follow for correctness.
Signed-off-by: Jérôme Glisse jglisse@redhat.com Cc: Steve French sfrench@samba.org Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Stable stable@vger.kernel.org
fs/cifs/file.c | 15 +-------------- fs/cifs/misc.c | 23 ++++++++++++++++++++++- 2 files changed, 23 insertions(+), 15 deletions(-)
diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 89006e044973..a756a4d3f70f 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -2858,7 +2858,6 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx) struct cifs_tcon *tcon; struct cifs_sb_info *cifs_sb; struct dentry *dentry = ctx->cfile->dentry;
unsigned int i; int rc; tcon = tlink_tcon(ctx->cfile->tlink);@@ -2922,10 +2921,6 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx) kref_put(&wdata->refcount, cifs_uncached_writedata_release); }
if (!ctx->direct_io)for (i = 0; i < ctx->npages; i++)put_page(ctx->bv[i].bv_page);cifs_stats_bytes_written(tcon, ctx->total_len); set_bit(CIFS_INO_INVALID_MAPPING, &CIFS_I(dentry->d_inode)->flags);@@ -3563,7 +3558,6 @@ collect_uncached_read_data(struct cifs_aio_ctx *ctx) struct iov_iter *to = &ctx->iter; struct cifs_sb_info *cifs_sb; struct cifs_tcon *tcon;
unsigned int i; int rc; tcon = tlink_tcon(ctx->cfile->tlink);@@ -3647,15 +3641,8 @@ collect_uncached_read_data(struct cifs_aio_ctx *ctx) kref_put(&rdata->refcount, cifs_uncached_readdata_release); }
if (!ctx->direct_io) {for (i = 0; i < ctx->npages; i++) {if (ctx->should_dirty)set_page_dirty(ctx->bv[i].bv_page);put_page(ctx->bv[i].bv_page);}
if (!ctx->direct_io) ctx->total_len = ctx->len - iov_iter_count(to);
} /* mask nodata case */ if (rc == -ENODATA)diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c index bee203055b30..9bc0d17a9d77 100644 --- a/fs/cifs/misc.c +++ b/fs/cifs/misc.c @@ -768,6 +768,11 @@ cifs_aio_ctx_alloc(void) { struct cifs_aio_ctx *ctx;
/** Must use kzalloc to initialize ctx->bv to NULL and ctx->direct_io* to false so that we know when we have to unreference pages within* cifs_aio_ctx_release()*/ ctx = kzalloc(sizeof(struct cifs_aio_ctx), GFP_KERNEL); if (!ctx) return NULL;@@ -786,7 +791,23 @@ cifs_aio_ctx_release(struct kref *refcount) struct cifs_aio_ctx, refcount);
cifsFileInfo_put(ctx->cfile);
kvfree(ctx->bv);
/** ctx->bv is only set if setup_aio_ctx_iter() was call successfuly* which means that iov_iter_get_pages() was a success and thus that* we have taken reference on pages.*/if (ctx->bv) {unsigned i;for (i = 0; i < ctx->npages; i++) {if (ctx->should_dirty)set_page_dirty(ctx->bv[i].bv_page);put_page(ctx->bv[i].bv_page);}kvfree(ctx->bv);}kfree(ctx);}
-- 2.20.1
-- Thanks,
Steve