From 9a7d5a9e6d7921e1854b4606ce8c3e17d565f463 Mon Sep 17 00:00:00 2001 From: Aurelien Aptel Date: Wed, 4 Dec 2019 16:14:54 +0100 Subject: cifs: fix possible uninitialized access and race on iface_list iface[0] was accessed regardless of the count value and without locking. * check count before accessing any ifaces * make copy of iface list (it's a simple POD array) and use it without locking. Signed-off-by: Aurelien Aptel Signed-off-by: Steve French Reviewed-by: Paulo Alcantara (SUSE) --- fs/cifs/sess.c | 29 ++++++++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-) (limited to 'fs') diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c index d95137304224..f0795c856d8f 100644 --- a/fs/cifs/sess.c +++ b/fs/cifs/sess.c @@ -77,6 +77,8 @@ int cifs_try_adding_channels(struct cifs_ses *ses) int i = 0; int rc = 0; int tries = 0; + struct cifs_server_iface *ifaces = NULL; + size_t iface_count; if (left <= 0) { cifs_dbg(FYI, @@ -90,6 +92,26 @@ int cifs_try_adding_channels(struct cifs_ses *ses) return 0; } + /* + * Make a copy of the iface list at the time and use that + * instead so as to not hold the iface spinlock for opening + * channels + */ + spin_lock(&ses->iface_lock); + iface_count = ses->iface_count; + if (iface_count <= 0) { + spin_unlock(&ses->iface_lock); + cifs_dbg(FYI, "no iface list available to open channels\n"); + return 0; + } + ifaces = kmemdup(ses->iface_list, iface_count*sizeof(*ifaces), + GFP_ATOMIC); + if (!ifaces) { + spin_unlock(&ses->iface_lock); + return 0; + } + spin_unlock(&ses->iface_lock); + /* * Keep connecting to same, fastest, iface for all channels as * long as its RSS. Try next fastest one if not RSS or channel @@ -105,9 +127,9 @@ int cifs_try_adding_channels(struct cifs_ses *ses) break; } - iface = &ses->iface_list[i]; + iface = &ifaces[i]; if (is_ses_using_iface(ses, iface) && !iface->rss_capable) { - i = (i+1) % ses->iface_count; + i = (i+1) % iface_count; continue; } @@ -115,7 +137,7 @@ int cifs_try_adding_channels(struct cifs_ses *ses) if (rc) { cifs_dbg(FYI, "failed to open extra channel on iface#%d rc=%d\n", i, rc); - i = (i+1) % ses->iface_count; + i = (i+1) % iface_count; continue; } @@ -124,6 +146,7 @@ int cifs_try_adding_channels(struct cifs_ses *ses) left--; } + kfree(ifaces); return ses->chan_count - old_chan_count; } -- cgit v1.2.3-59-g8ed1b