| Message ID | 1466340570-2471502-1-git-send-email-yigal@plexistor.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Jun 19, 2016 at 5:49 AM, Yigal Korman <yigal@plexistor.com> wrote: > Before this patch, passing a range that is beyond the physical memory > range will succeed, the user will see a /dev/pmem0 and will be able to > access it. Reads will always return 0 and writes will be silently > ignored. > > I've gotten more than one bug report about mkfs.{xfs,ext4} or nvml > failing that were eventually tracked down to be wrong values passed to > memmap. > > This patch prevents the above issue by instead of adding a new memory > range, only update a RAM memory range with the PRAM type. This way, > passing the wrong memmap will either not give you a pmem at all or give > you a smaller one that actually has RAM behind it. > > And if someone still needs to fake a pmem that doesn't have RAM behind > it, they can simply do memmap=XX@YY,XX!YY. Thanks! I've debugged a report like this as well.
Hi, I've sent this to the wrong maintainer by mistake (sorry about that) so I going to re-post it again in a moment. FYI Thanks, Yigal On Sun, Jun 19, 2016 at 7:40 PM, Dan Williams <dan.j.williams@intel.com> wrote: > On Sun, Jun 19, 2016 at 5:49 AM, Yigal Korman <yigal@plexistor.com> wrote: >> Before this patch, passing a range that is beyond the physical memory >> range will succeed, the user will see a /dev/pmem0 and will be able to >> access it. Reads will always return 0 and writes will be silently >> ignored. >> >> I've gotten more than one bug report about mkfs.{xfs,ext4} or nvml >> failing that were eventually tracked down to be wrong values passed to >> memmap. >> >> This patch prevents the above issue by instead of adding a new memory >> range, only update a RAM memory range with the PRAM type. This way, >> passing the wrong memmap will either not give you a pmem at all or give >> you a smaller one that actually has RAM behind it. >> >> And if someone still needs to fake a pmem that doesn't have RAM behind >> it, they can simply do memmap=XX@YY,XX!YY. > > Thanks! I've debugged a report like this as well.
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c index 569c1e4..bcd2ebb1 100644 --- a/arch/x86/kernel/e820.c +++ b/arch/x86/kernel/e820.c @@ -877,7 +877,7 @@ static int __init parse_memmap_one(char *p) e820_add_region(start_at, mem_size, E820_RESERVED); } else if (*p == '!') { start_at = memparse(p+1, &p); - e820_add_region(start_at, mem_size, E820_PRAM); + e820_update_range(start_at, mem_size, E820_RAM, E820_PRAM); } else e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
Before this patch, passing a range that is beyond the physical memory range will succeed, the user will see a /dev/pmem0 and will be able to access it. Reads will always return 0 and writes will be silently ignored. I've gotten more than one bug report about mkfs.{xfs,ext4} or nvml failing that were eventually tracked down to be wrong values passed to memmap. This patch prevents the above issue by instead of adding a new memory range, only update a RAM memory range with the PRAM type. This way, passing the wrong memmap will either not give you a pmem at all or give you a smaller one that actually has RAM behind it. And if someone still needs to fake a pmem that doesn't have RAM behind it, they can simply do memmap=XX@YY,XX!YY. Signed-off-by: Yigal Korman <yigal@plexistor.com> --- arch/x86/kernel/e820.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)