From f2ca862debd8b9875b5448553be0f2178fc4231f Mon Sep 17 00:00:00 2001 From: Steve French Date: Tue, 6 Feb 2024 16:34:22 -0600 Subject: [PATCH] smb: Fix regression in writes when non-standard maximum write size negotiated The conversion to netfs in the 6.3 kernel caused a regression when maximum write size is set by the server to an unexpected value which is not a multiple of 4096 (similarly if the user overrides the maximum write size by setting mount parm "wsize", but sets it to a value that is not a multiple of 4096). When negotiated write size is not a multiple of 4096 the netfs code can skip the end of the final page when doing large sequential writes, causing data corruption. This section of code is being rewritten/removed due to a large netfs change, but until that point (ie for the 6.3 kernel until now) we can not support non-standard maximum write sizes. Add a warning if a user specifies a wsize on mount that is not a multiple of 4096, and also add a change where we round down the maximum write size if the server negotiates a value that is not a multiple of 4096 (we also have to check to make sure that we do not round it down to zero). Reported-by: R. Diez" Fixes: d08089f649a0 ("cifs: Change the I/O paths to use an iterator rather than a page list") Suggested-by: Ronnie Sahlberg Cc: stable@vger.kernel.org # v6.3+ Cc: David Howells Signed-off-by: Steve French --- fs/smb/client/connect.c | 13 +++++++++++-- fs/smb/client/fs_context.c | 2 ++ 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c index bfd568f89710..46b3aeebfbf2 100644 --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -3438,8 +3438,17 @@ int cifs_mount_get_tcon(struct cifs_mount_ctx *mnt_ctx) * the user on mount */ if ((cifs_sb->ctx->wsize == 0) || - (cifs_sb->ctx->wsize > server->ops->negotiate_wsize(tcon, ctx))) - cifs_sb->ctx->wsize = server->ops->negotiate_wsize(tcon, ctx); + (cifs_sb->ctx->wsize > server->ops->negotiate_wsize(tcon, ctx))) { + cifs_sb->ctx->wsize = round_down(server->ops->negotiate_wsize(tcon, ctx), 4096); + /* + * in the very unlikely event that the server sent a max write size under 4K, + * (which would get rounded down to 0) then reset wsize to absolute minimum ie 4096 + */ + if (cifs_sb->ctx->wsize == 0) { + cifs_sb->ctx->wsize = 4096; + cifs_dbg(VFS, "wsize too small, reset to minimum ie 4096\n"); + } + } if ((cifs_sb->ctx->rsize == 0) || (cifs_sb->ctx->rsize > server->ops->negotiate_rsize(tcon, ctx))) cifs_sb->ctx->rsize = server->ops->negotiate_rsize(tcon, ctx); diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c index 52cbef2eeb28..600a77052c3b 100644 --- a/fs/smb/client/fs_context.c +++ b/fs/smb/client/fs_context.c @@ -1111,6 +1111,8 @@ static int smb3_fs_context_parse_param(struct fs_context *fc, case Opt_wsize: ctx->wsize = result.uint_32; ctx->got_wsize = true; + if (round_up(ctx->wsize, 4096) != ctx->wsize) + cifs_dbg(VFS, "wsize should be a multiple of 4096\n"); break; case Opt_acregmax: ctx->acregmax = HZ * result.uint_32; -- 2.40.1