https://github.com/torvalds/linux
Revision c1e63117711977cc4295b2ce73de29dd17066c82 authored by David Hildenbrand on 20 November 2021, 00:43:58 UTC, committed by Linus Torvalds on 20 November 2021, 18:35:55 UTC
To clear a user buffer we cannot simply use memset, we have to use clear_user(). With a virtio-mem device that registers a vmcore_cb and has some logically unplugged memory inside an added Linux memory block, I can easily trigger a BUG by copying the vmcore via "cp": systemd[1]: Starting Kdump Vmcore Save Service... kdump[420]: Kdump is using the default log level(3). kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[465]: saving vmcore-dmesg.txt complete kdump[467]: saving vmcore BUG: unable to handle page fault for address: 00007f2374e01000 #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867 Oops: 0003 [#1] PREEMPT SMP NOPTI CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014 RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86 Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 <49> c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81 RSP: 0018:ffffc9000073be08 EFLAGS: 00010212 RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000 RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008 RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50 R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000 R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8 FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0 Call Trace: read_vmcore+0x236/0x2c0 proc_reg_read+0x55/0xa0 vfs_read+0x95/0x190 ksys_read+0x4f/0xc0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Some x86-64 CPUs have a CPU feature called "Supervisor Mode Access Prevention (SMAP)", which is used to detect wrong access from the kernel to user buffers like this: SMAP triggers a permissions violation on wrong access. In the x86-64 variant of clear_user(), SMAP is properly handled via clac()+stac(). To fix, properly use clear_user() when we're dealing with a user buffer. Link: https://lkml.kernel.org/r/20211112092750.6921-1-david@redhat.com Fixes: 997c136f518c ("fs/proc/vmcore.c: add hook to read_from_oldmem() to check for non-ram pages") Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Baoquan He <bhe@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Philipp Rudo <prudo@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 825c43f
Tip revision: c1e63117711977cc4295b2ce73de29dd17066c82 authored by David Hildenbrand on 20 November 2021, 00:43:58 UTC
proc/vmcore: fix clearing user buffer by properly using clear_user()
proc/vmcore: fix clearing user buffer by properly using clear_user()
Tip revision: c1e6311
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kunit | ||
livepatch | ||
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math | ||
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test_fortify | ||
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Kconfig.debug | -rw-r--r-- | 86.1 KB |
Kconfig.kasan | -rw-r--r-- | 7.3 KB |
Kconfig.kcsan | -rw-r--r-- | 9.5 KB |
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Kconfig.kgdb | -rw-r--r-- | 5.6 KB |
Kconfig.ubsan | -rw-r--r-- | 6.3 KB |
Makefile | -rw-r--r-- | 13.3 KB |
argv_split.c | -rw-r--r-- | 2.1 KB |
ashldi3.c | -rw-r--r-- | 541 bytes |
ashrdi3.c | -rw-r--r-- | 565 bytes |
asn1_decoder.c | -rw-r--r-- | 13.2 KB |
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assoc_array.c | -rw-r--r-- | 51.7 KB |
atomic64.c | -rw-r--r-- | 4.6 KB |
atomic64_test.c | -rw-r--r-- | 6.4 KB |
audit.c | -rw-r--r-- | 1.9 KB |
bcd.c | -rw-r--r-- | 297 bytes |
bch.c | -rw-r--r-- | 38.3 KB |
bitfield_kunit.c | -rw-r--r-- | 4.4 KB |
bitmap.c | -rw-r--r-- | 44.9 KB |
bitrev.c | -rw-r--r-- | 1.9 KB |
bootconfig.c | -rw-r--r-- | 21.1 KB |
bsearch.c | -rw-r--r-- | 1.2 KB |
btree.c | -rw-r--r-- | 19.2 KB |
bucket_locks.c | -rw-r--r-- | 1.4 KB |
bug.c | -rw-r--r-- | 5.9 KB |
build_OID_registry | -rwxr-xr-x | 4.5 KB |
buildid.c | -rw-r--r-- | 5.0 KB |
bust_spinlocks.c | -rw-r--r-- | 676 bytes |
check_signature.c | -rw-r--r-- | 635 bytes |
checksum.c | -rw-r--r-- | 4.1 KB |
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clz_tab.c | -rw-r--r-- | 891 bytes |
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cmdline_kunit.c | -rw-r--r-- | 4.2 KB |
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crc-itu-t.c | -rw-r--r-- | 2.7 KB |
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kobject.c | -rw-r--r-- | 28.2 KB |
kobject_uevent.c | -rw-r--r-- | 18.9 KB |
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llist.c | -rw-r--r-- | 2.5 KB |
locking-selftest-hardirq.h | -rw-r--r-- | 246 bytes |
locking-selftest-mutex.h | -rw-r--r-- | 159 bytes |
locking-selftest-rlock-hardirq.h | -rw-r--r-- | 74 bytes |
locking-selftest-rlock-softirq.h | -rw-r--r-- | 74 bytes |
locking-selftest-rlock.h | -rw-r--r-- | 197 bytes |
locking-selftest-rsem.h | -rw-r--r-- | 202 bytes |
locking-selftest-rtmutex.h | -rw-r--r-- | 162 bytes |
locking-selftest-softirq.h | -rw-r--r-- | 246 bytes |
locking-selftest-spin-hardirq.h | -rw-r--r-- | 73 bytes |
locking-selftest-spin-softirq.h | -rw-r--r-- | 73 bytes |
locking-selftest-spin.h | -rw-r--r-- | 157 bytes |
locking-selftest-wlock-hardirq.h | -rw-r--r-- | 74 bytes |
locking-selftest-wlock-softirq.h | -rw-r--r-- | 74 bytes |
locking-selftest-wlock.h | -rw-r--r-- | 197 bytes |
locking-selftest-wsem.h | -rw-r--r-- | 202 bytes |
locking-selftest.c | -rw-r--r-- | 63.7 KB |
lockref.c | -rw-r--r-- | 4.5 KB |
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logic_pio.c | -rw-r--r-- | 8.5 KB |
lru_cache.c | -rw-r--r-- | 18.8 KB |
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memcat_p.c | -rw-r--r-- | 753 bytes |
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memory-notifier-error-inject.c | -rw-r--r-- | 1.1 KB |
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sha1.c | -rw-r--r-- | 6.3 KB |
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test_siphash.c | -rw-r--r-- | 7.5 KB |
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test_string.c | -rw-r--r-- | 3.9 KB |
test_strscpy.c | -rw-r--r-- | 4.0 KB |
test_sysctl.c | -rw-r--r-- | 3.9 KB |
test_ubsan.c | -rw-r--r-- | 2.9 KB |
test_user_copy.c | -rw-r--r-- | 9.1 KB |
test_uuid.c | -rw-r--r-- | 3.4 KB |
test_vmalloc.c | -rw-r--r-- | 10.9 KB |
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