Buildresult: linus/um-defconfig/um-x86_64 built on Mar 30 2022, 12:26

kisskb

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Status:	OK
Date/Time:	Mar 30 2022, 12:26
Duration:	0:00:51.452983
Builder:	ka4
Revision:	fs: fd tables have to be multiples of BITS_PER_LONG (`1c24a186398f59c80adb9a967486b65c1423a59d)`
Target:	linus/um-defconfig/um-x86_64
Branch:	linus
Compiler:	um-x86_64 (x86_64-linux-gcc.br_real (Buildroot 2017.05) 5.4.0 / GNU ld (GNU Binutils) 2.27)
Config:	defconfig (download)
Log:	Download original No warnings found in log. Full Log # git rev-parse -q --verify 1c24a186398f59c80adb9a967486b65c1423a59d^{commit} 1c24a186398f59c80adb9a967486b65c1423a59d already have revision, skipping fetch # git checkout -q -f -B kisskb 1c24a186398f59c80adb9a967486b65c1423a59d # git clean -qxdf # < git log -1 # commit 1c24a186398f59c80adb9a967486b65c1423a59d # Author: Linus Torvalds <torvalds@linux-foundation.org> # Date: Tue Mar 29 15:06:39 2022 -0700 # # fs: fd tables have to be multiples of BITS_PER_LONG # # This has always been the rule: fdtables have several bitmaps in them, # and as a result they have to be sized properly for bitmaps. We walk # those bitmaps in chunks of 'unsigned long' in serveral cases, but even # when we don't, we use the regular kernel bitops that are defined to work # on arrays of 'unsigned long', not on some byte array. # # Now, the distinction between arrays of bytes and 'unsigned long' # normally only really ends up being noticeable on big-endian systems, but # Fedor Pchelkin and Alexey Khoroshilov reported that copy_fd_bitmaps() # could be called with an argument that wasn't even a multiple of # BITS_PER_BYTE. And then it fails to do the proper copy even on # little-endian machines. # # The bug wasn't in copy_fd_bitmap(), but in sane_fdtable_size(), which # didn't actually sanitize the fdtable size sufficiently, and never made # sure it had the proper BITS_PER_LONG alignment. # # That's partly because the alignment historically came not from having to # explicitly align things, but simply from previous fdtable sizes, and # from count_open_files(), which counts the file descriptors by walking # them one 'unsigned long' word at a time and thus naturally ends up doing # sizing in the proper 'chunks of unsigned long'. # # But with the introduction of close_range(), we now have an external # source of "this is how many files we want to have", and so # sane_fdtable_size() needs to do a better job. # # This also adds that explicit alignment to alloc_fdtable(), although # there it is mainly just for documentation at a source code level. The # arithmetic we do there to pick a reasonable fdtable size already aligns # the result sufficiently. # # In fact,clang notices that the added ALIGN() in that function doesn't # actually do anything, and does not generate any extra code for it. # # It turns out that gcc ends up confusing itself by combining a previous # constant-sized shift operation with the variable-sized shift operations # in roundup_pow_of_two(). And probably due to that doesn't notice that # the ALIGN() is a no-op. But that's a (tiny) gcc misfeature that doesn't # matter. Having the explicit alignment makes sense, and would actually # matter on a 128-bit architecture if we ever go there. # # This also adds big comments above both functions about how fdtable sizes # have to have that BITS_PER_LONG alignment. # # Fixes: 60997c3d45d9 ("close_range: add CLOSE_RANGE_UNSHARE") # Reported-by: Fedor Pchelkin <aissur0002@gmail.com> # Reported-by: Alexey Khoroshilov <khoroshilov@ispras.ru> # Link: https://lore.kernel.org/all/20220326114009.1690-1-aissur0002@gmail.com/ # Tested-and-acked-by: Christian Brauner <brauner@kernel.org> # Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> # < /opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux-gcc --version # < /opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux-ld --version # < git log --format=%s --max-count=1 1c24a186398f59c80adb9a967486b65c1423a59d # < make -s -j 10 ARCH=um O=/kisskb/build/linus_um-defconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 defconfig # < make -s -j 10 ARCH=um O=/kisskb/build/linus_um-defconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 help # make -s -j 10 ARCH=um O=/kisskb/build/linus_um-defconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 olddefconfig # make -s -j 10 ARCH=um O=/kisskb/build/linus_um-defconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 LINK linux Completed OK # rm -rf /kisskb/build/linus_um-defconfig_um-x86_64 # Build took: 0:00:51.452983

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