diff options
| author | Michael Karcher <kernel@mkarcher.dialup.fu-berlin.de> | 2025-09-05 00:03:31 +0200 |
|---|---|---|
| committer | Andreas Larsson <andreas@gaisler.com> | 2025-09-19 20:56:36 +0200 |
| commit | 47b49c06eb62504075f0f2e2227aee2e2c2a58b3 (patch) | |
| tree | 49eda0ef7705fcdb6f029ea59afb1e0a4edaea2f | |
| parent | 4fba1713001195e59cfc001ff1f2837dab877efb (diff) | |
sparc: fix accurate exception reporting in copy_{from_to}_user for UltraSPARC III
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@physik.fu-berlin.de
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.dialup.fu-berlin.de
Signed-off-by: Andreas Larsson <andreas@gaisler.com>
| -rw-r--r-- | arch/sparc/lib/U3memcpy.S | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/sparc/lib/U3memcpy.S b/arch/sparc/lib/U3memcpy.S index 9248d59c734c..bace3a18f836 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 |