This is a note to let you know that I've just added the patch titled PCI: rpadlpar: Fix potential drc_name corruption in store functions to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: pci-rpadlpar-fix-potential-drc_name-corruption-in-store-functions.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From cc7a0bb058b85ea03db87169c60c7cfdd5d34678 Mon Sep 17 00:00:00 2001 From: Tyrel Datwyler <tyreld@xxxxxxxxxxxxx> Date: Mon, 15 Mar 2021 15:48:21 -0600 Subject: PCI: rpadlpar: Fix potential drc_name corruption in store functions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Tyrel Datwyler <tyreld@xxxxxxxxxxxxx> commit cc7a0bb058b85ea03db87169c60c7cfdd5d34678 upstream. Both add_slot_store() and remove_slot_store() try to fix up the drc_name copied from the store buffer by placing a NUL terminator at nbyte + 1 or in place of a '\n' if present. However, the static buffer that we copy the drc_name data into is not zeroed and can contain anything past the n-th byte. This is problematic if a '\n' byte appears in that buffer after nbytes and the string copied into the store buffer was not NUL terminated to start with as the strchr() search for a '\n' byte will mark this incorrectly as the end of the drc_name string resulting in a drc_name string that contains garbage data after the n-th byte. Additionally it will cause us to overwrite that '\n' byte on the stack with NUL, potentially corrupting data on the stack. The following debugging shows an example of the drmgr utility writing "PHB 4543" to the add_slot sysfs attribute, but add_slot_store() logging a corrupted string value. drmgr: drmgr: -c phb -a -s PHB 4543 -d 1 add_slot_store: drc_name = PHB 4543°|<82>!, rc = -19 Fix this by using strscpy() instead of memcpy() to ensure the string is NUL terminated when copied into the static drc_name buffer. Further, since the string is now NUL terminated the code only needs to change '\n' to '\0' when present. Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Tyrel Datwyler <tyreld@xxxxxxxxxxxxx> [mpe: Reformat change log and add mention of possible stack corruption] Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210315214821.452959-1-tyreld@xxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/pci/hotplug/rpadlpar_sysfs.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) --- a/drivers/pci/hotplug/rpadlpar_sysfs.c +++ b/drivers/pci/hotplug/rpadlpar_sysfs.c @@ -34,12 +34,11 @@ static ssize_t add_slot_store(struct kob if (nbytes >= MAX_DRC_NAME_LEN) return 0; - memcpy(drc_name, buf, nbytes); + strscpy(drc_name, buf, nbytes + 1); end = strchr(drc_name, '\n'); - if (!end) - end = &drc_name[nbytes]; - *end = '\0'; + if (end) + *end = '\0'; rc = dlpar_add_slot(drc_name); if (rc) @@ -65,12 +64,11 @@ static ssize_t remove_slot_store(struct if (nbytes >= MAX_DRC_NAME_LEN) return 0; - memcpy(drc_name, buf, nbytes); + strscpy(drc_name, buf, nbytes + 1); end = strchr(drc_name, '\n'); - if (!end) - end = &drc_name[nbytes]; - *end = '\0'; + if (end) + *end = '\0'; rc = dlpar_remove_slot(drc_name); if (rc) Patches currently in stable-queue which might be from tyreld@xxxxxxxxxxxxx are queue-5.11/pci-rpadlpar-fix-potential-drc_name-corruption-in-store-functions.patch