5.15-stable review patch. If anyone has any objections, please let me know.
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From: Michael Karcher kernel@mkarcher.dialup.fu-berlin.de
[ Upstream commit 47b49c06eb62504075f0f2e2227aee2e2c2a58b3 ]
Anthony Yznaga tracked down that a BUG_ON in ext4 code with large folios enabled resulted from copy_from_user() returning impossibly large values greater than the size to be copied. This lead to __copy_from_iter() returning impossible values instead of the actual number of bytes it was able to copy.
The BUG_ON has been reported in https://lore.kernel.org/r/b14f55642207e63e907965e209f6323a0df6dcee.camel@phy...
The referenced commit introduced exception handlers on user-space memory references in copy_from_user and copy_to_user. These handlers return from the respective function and calculate the remaining bytes left to copy using the current register contents. The exception handlers expect that %o2 has already been masked during the bulk copy loop, but the masking was performed after that loop. This will fix the return value of copy_from_user and copy_to_user in the faulting case. The behaviour of memcpy stays unchanged.
Fixes: ee841d0aff64 ("sparc64: Convert U3copy_{from,to}_user to accurate exception reporting.") Tested-by: John Paul Adrian Glaubitz glaubitz@physik.fu-berlin.de # on Sun Netra 240 Reviewed-by: Anthony Yznaga anthony.yznaga@oracle.com Tested-by: René Rebe rene@exactcode.com # on UltraSparc III+ and UltraSparc IIIi Signed-off-by: Michael Karcher kernel@mkarcher.dialup.fu-berlin.de Reviewed-by: Andreas Larsson andreas@gaisler.com Link: https://lore.kernel.org/r/20250905-memcpy_series-v4-2-1ca72dda195b@mkarcher.... Signed-off-by: Andreas Larsson andreas@gaisler.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/sparc/lib/U3memcpy.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/sparc/lib/U3memcpy.S b/arch/sparc/lib/U3memcpy.S index 9248d59c734ce..bace3a18f836f 100644 --- a/arch/sparc/lib/U3memcpy.S +++ b/arch/sparc/lib/U3memcpy.S @@ -267,6 +267,7 @@ FUNC_NAME: /* %o0=dst, %o1=src, %o2=len */ faligndata %f10, %f12, %f26 EX_LD_FP(LOAD(ldd, %o1 + 0x040, %f0), U3_retl_o2)
+ and %o2, 0x3f, %o2 subcc GLOBAL_SPARE, 0x80, GLOBAL_SPARE add %o1, 0x40, %o1 bgu,pt %XCC, 1f @@ -336,7 +337,6 @@ FUNC_NAME: /* %o0=dst, %o1=src, %o2=len */ * Also notice how this code is careful not to perform a * load past the end of the src buffer. */ - and %o2, 0x3f, %o2 andcc %o2, 0x38, %g2 be,pn %XCC, 2f subcc %g2, 0x8, %g2