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[166.176.184.21]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-302978b1a79sm14940844eec.28.2026.05.18.17.14.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 May 2026 17:14:59 -0700 (PDT) From: Fredric Cover X-Google-Original-From: Fredric Cover To: sfrench@samba.org Cc: pc@manguebit.com, ronniesahlberg@gmail.com, sprasad@microsoft.com, tom@talpey.com, bharathsm@microsoft.com, linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org, Fredric Cover Subject: [PATCH] smb: client: fix memory corruption in smb3_reconfigure() Date: Mon, 18 May 2026 17:12:41 -0700 Message-ID: <20260519001241.553855-1-FredTheDude@proton.me> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Fredric Cover smb3_reconfigure() modifies the active volume context directly. If smb3_fs_context_dup() fails to allocate space when copying strings of a new context into the volume context, it clears the volume context. Add staging logic (tmp_ctx) to ensure that either the volume context stays the same on errors or is updated with the new state, and is never cleared. Signed-off-by: Fredric Cover --- fs/smb/client/fs_context.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c index b9544eb03..3a6f207a5 100644 --- a/fs/smb/client/fs_context.c +++ b/fs/smb/client/fs_context.c @@ -1082,6 +1082,7 @@ static void smb3_sync_ses_chan_max(struct cifs_ses *s= es, unsigned int max_channe static int smb3_reconfigure(struct fs_context *fc) { struct smb3_fs_context *ctx =3D smb3_fc2context(fc); + struct smb3_fs_context *tmp_ctx; /* used for copy of ctx to cifs_sb->ctx = */ struct dentry *root =3D fc->root; struct cifs_sb_info *cifs_sb =3D CIFS_SB(root->d_sb); struct cifs_ses *ses =3D cifs_sb_master_tcon(cifs_sb)->ses; @@ -1205,13 +1206,19 @@ static int smb3_reconfigure(struct fs_context *fc) ctx->rsize =3D rsize ? CIFS_ALIGN_RSIZE(fc, rsize) : cifs_sb->ctx->rsize; ctx->wsize =3D wsize ? CIFS_ALIGN_WSIZE(fc, wsize) : cifs_sb->ctx->wsize; =20 - smb3_cleanup_fs_context_contents(cifs_sb->ctx); - rc =3D smb3_fs_context_dup(cifs_sb->ctx, ctx); - smb3_update_mnt_flags(cifs_sb); + tmp_ctx =3D kzalloc_obj(*tmp_ctx, GFP_KERNEL); + if (!tmp_ctx) + return -ENOMEM; + rc =3D smb3_fs_context_dup(tmp_ctx, ctx); + if (!rc) { + smb3_cleanup_fs_context_contents(cifs_sb->ctx); + memcpy(cifs_sb->ctx, tmp_ctx, sizeof(*tmp_ctx)); + smb3_update_mnt_flags(cifs_sb); #ifdef CONFIG_CIFS_DFS_UPCALL - if (!rc) rc =3D dfs_cache_remount_fs(cifs_sb); #endif + } + kfree(tmp_ctx); =20 return rc; } --=20 2.53.0