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authorMatt Redfearn <matt.redfearn@mips.com>2018-04-17 15:52:21 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-04-24 09:34:17 +0200
commit6cd712bfbbf1957289ad906d4d6191c1a3fc31a1 (patch)
parent7177f0b3a8585687abf28234edb80fe209ac2f62 (diff)
MIPS: memset.S: Fix return of __clear_user from Lpartial_fixup
commit daf70d89f80c6e1772233da9e020114b1254e7e0 upstream. The __clear_user function is defined to return the number of bytes that could not be cleared. From the underlying memset / bzero implementation this means setting register a2 to that number on return. Currently if a page fault is triggered within the memset_partial block, the value loaded into a2 on return is meaningless. The label .Lpartial_fixup\@ is jumped to on page fault. In order to work out how many bytes failed to copy, the exception handler should find how many bytes left in the partial block (andi a2, STORMASK), add that to the partial block end address (a2), and subtract the faulting address to get the remainder. Currently it incorrectly subtracts the partial block start address (t1), which has additionally been clobbered to generate a jump target in memset_partial. Fix this by adding the block end address instead. This issue was found with the following test code: int j, k; for (j = 0; j < 512; j++) { if ((k = clear_user(NULL, j)) != j) { pr_err("clear_user (NULL %d) returned %d\n", j, k); } } Which now passes on Creator Ci40 (MIPS32) and Cavium Octeon II (MIPS64). Suggested-by: James Hogan <jhogan@kernel.org> Signed-off-by: Matt Redfearn <matt.redfearn@mips.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/19108/ Signed-off-by: James Hogan <jhogan@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/mips/lib/memset.S b/arch/mips/lib/memset.S
index 442197eea2fe..c6b2e3178b26 100644
--- a/arch/mips/lib/memset.S
+++ b/arch/mips/lib/memset.S
@@ -251,7 +251,7 @@
PTR_L t0, TI_TASK($28)
andi a2, STORMASK
- LONG_ADDU a2, t1
+ LONG_ADDU a2, a0
jr ra
LONG_SUBU a2, t0