| Message ID | 20210315214821.452959-1-tyreld@linux.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | cc7a0bb058b85ea03db87169c60c7cfdd5d34678 |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | [v2] rpadlpar: fix potential drc_name corruption in store functions | expand |
On Mon, 15 Mar 2021 15:48:21 -0600, Tyrel Datwyler wrote: > Both add_slot_store() and remove_slot_store() try to fix up the drc_name > copied from the store buffer by placing a NULL 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 zeored 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 NULL > 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. 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. > > [...] Applied to powerpc/fixes. [1/1] rpadlpar: fix potential drc_name corruption in store functions https://git.kernel.org/powerpc/c/cc7a0bb058b85ea03db87169c60c7cfdd5d34678 cheers
diff --git a/drivers/pci/hotplug/rpadlpar_sysfs.c b/drivers/pci/hotplug/rpadlpar_sysfs.c index cdbfa5df3a51..dbfa0b55d31a 100644 --- 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 kobject *kobj, struct kobj_attribute *attr, 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 kobject *kobj, 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)
Both add_slot_store() and remove_slot_store() try to fix up the drc_name copied from the store buffer by placing a NULL 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 zeored 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 NULL 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. 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. [135823.702864] drmgr: drmgr: -c phb -a -s PHB 4543 -d 1 [135823.702879] add_slot_store: drc_name = PHB 4543°|<82>!, rc = -19 Fix this by using strscpy() instead of memcpy() to ensure the string is NULL terminated when copied into the static drc_name buffer. Further, since the string is now NULL terminated the code only needs to change '\n' to '\0' when present. Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com> --- Changes in v2: * use strscpy instead of memcpy (suggested by mpe) drivers/pci/hotplug/rpadlpar_sysfs.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-)