From: Robert Richter rrichter@marvell.com
commit 216aa145aaf379a50b17afc812db71d893bd6683 upstream.
A test kernel with the options DEBUG_TEST_DRIVER_REMOVE, KASAN and DEBUG_KMEMLEAK set, revealed several issues when removing an mci device:
1) Use-after-free:
On 27.11.19 17:07:33, John Garry wrote:
[ 22.104498] BUG: KASAN: use-after-free in edac_remove_sysfs_mci_device+0x148/0x180
The use-after-free is caused by the mci_for_each_dimm() macro called in edac_remove_sysfs_mci_device(). The iterator was introduced with
c498afaf7df8 ("EDAC: Introduce an mci_for_each_dimm() iterator").
The iterator loop calls device_unregister(&dimm->dev), which removes the sysfs entry of the device, but also frees the dimm struct in dimm_attr_release(). When incrementing the loop in mci_for_each_dimm(), the dimm struct is accessed again, after having been freed already.
The fix is to free all the mci device's subsequent dimm and csrow objects at a later point, in _edac_mc_free(), when the mci device itself is being freed.
This keeps the data structures intact and the mci device can be fully used until its removal. The change allows the safe usage of mci_for_each_dimm() to release dimm devices from sysfs.
2) Memory leaks:
Following memory leaks have been detected:
# grep edac /sys/kernel/debug/kmemleak | sort | uniq -c 1 [<000000003c0f58f9>] edac_mc_alloc+0x3bc/0x9d0 # mci->csrows 16 [<00000000bb932dc0>] edac_mc_alloc+0x49c/0x9d0 # csr->channels 16 [<00000000e2734dba>] edac_mc_alloc+0x518/0x9d0 # csr->channels[chn] 1 [<00000000eb040168>] edac_mc_alloc+0x5c8/0x9d0 # mci->dimms 34 [<00000000ef737c29>] ghes_edac_register+0x1c8/0x3f8 # see edac_mc_alloc()
All leaks are from memory allocated by edac_mc_alloc().
Note: The test above shows that edac_mc_alloc() was called here from ghes_edac_register(), thus both functions show up in the stack trace but the module causing the leaks is edac_mc. The comments with the data structures involved were made manually by analyzing the objdump.
The data structures listed above and created by edac_mc_alloc() are not properly removed during device removal, which is done in edac_mc_free().
There are two paths implemented to remove the device depending on device registration, _edac_mc_free() is called if the device is not registered and edac_unregister_sysfs() otherwise.
The implemenations differ. For the sysfs case, the mci device removal lacks the removal of subsequent data structures (csrows, channels, dimms). This causes the memory leaks (see mci_attr_release()).
[ bp: Massage commit message. ]
Fixes: c498afaf7df8 ("EDAC: Introduce an mci_for_each_dimm() iterator") Fixes: faa2ad09c01c ("edac_mc: edac_mc_free() cannot assume mem_ctl_info is registered in sysfs.") Fixes: 7a623c039075 ("edac: rewrite the sysfs code to use struct device") Reported-by: John Garry john.garry@huawei.com Signed-off-by: Robert Richter rrichter@marvell.com Signed-off-by: Borislav Petkov bp@suse.de Tested-by: John Garry john.garry@huawei.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200212120340.4764-3-rrichter@marvell.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/edac/edac_mc.c | 12 +++--------- drivers/edac/edac_mc_sysfs.c | 15 +++------------ 2 files changed, 6 insertions(+), 21 deletions(-)
--- a/drivers/edac/edac_mc.c +++ b/drivers/edac/edac_mc.c @@ -503,16 +503,10 @@ void edac_mc_free(struct mem_ctl_info *m { edac_dbg(1, "\n");
- /* If we're not yet registered with sysfs free only what was allocated - * in edac_mc_alloc(). - */ - if (!device_is_registered(&mci->dev)) { - _edac_mc_free(mci); - return; - } + if (device_is_registered(&mci->dev)) + edac_unregister_sysfs(mci);
- /* the mci instance is freed here, when the sysfs object is dropped */ - edac_unregister_sysfs(mci); + _edac_mc_free(mci); } EXPORT_SYMBOL_GPL(edac_mc_free);
--- a/drivers/edac/edac_mc_sysfs.c +++ b/drivers/edac/edac_mc_sysfs.c @@ -276,10 +276,7 @@ static const struct attribute_group *csr
static void csrow_attr_release(struct device *dev) { - struct csrow_info *csrow = container_of(dev, struct csrow_info, dev); - - edac_dbg(1, "device %s released\n", dev_name(dev)); - kfree(csrow); + /* release device with _edac_mc_free() */ }
static const struct device_type csrow_attr_type = { @@ -619,10 +616,7 @@ static const struct attribute_group *dim
static void dimm_attr_release(struct device *dev) { - struct dimm_info *dimm = container_of(dev, struct dimm_info, dev); - - edac_dbg(1, "device %s released\n", dev_name(dev)); - kfree(dimm); + /* release device with _edac_mc_free() */ }
static const struct device_type dimm_attr_type = { @@ -905,10 +899,7 @@ static const struct attribute_group *mci
static void mci_attr_release(struct device *dev) { - struct mem_ctl_info *mci = container_of(dev, struct mem_ctl_info, dev); - - edac_dbg(1, "device %s released\n", dev_name(dev)); - kfree(mci); + /* release device with _edac_mc_free() */ }
static const struct device_type mci_attr_type = {