# git rev-parse -q --verify 3593030761630e09200072a4bd06468892c27be3^{commit} 3593030761630e09200072a4bd06468892c27be3 already have revision, skipping fetch # git checkout -q -f -B kisskb 3593030761630e09200072a4bd06468892c27be3 # git clean -qxdf # < git log -1 # commit 3593030761630e09200072a4bd06468892c27be3 # Author: Linus Torvalds # Date: Tue Feb 15 15:28:00 2022 -0800 # # tty: n_tty: do not look ahead for EOL character past the end of the buffer # # Daniel Gibson reports that the n_tty code gets line termination wrong in # very specific cases: # # "If you feed a line with exactly 64 chars + terminating newline, and # directly afterwards (without reading) another line into a pseudo # terminal, the the first read() on the other side will return the 64 # char line *without* terminating newline, and the next read() will # return the missing terminating newline AND the complete next line (if # it fits in the buffer)" # # and bisected the behavior to commit 3b830a9c34d5 ("tty: convert # tty_ldisc_ops 'read()' function to take a kernel pointer"). # # Now, digging deeper, it turns out that the behavior isn't exactly new: # what changed in commit 3b830a9c34d5 was that the tty line discipline # .read() function is now passed an intermediate kernel buffer rather than # the final user space buffer. # # And that intermediate kernel buffer is 64 bytes in size - thus that # special case with exactly 64 bytes plus terminating newline. # # The same problem did exist before, but historically the boundary was not # the 64-byte chunk, but the user-supplied buffer size, which is obviously # generally bigger (and potentially bigger than N_TTY_BUF_SIZE, which # would hide the issue entirely). # # The reason is that the n_tty canon_copy_from_read_buf() code would look # ahead for the EOL character one byte further than it would actually # copy. It would then decide that it had found the terminator, and unmark # it as an EOL character - which in turn explains why the next read # wouldn't then be terminated by it. # # Now, the reason it did all this in the first place is related to some # historical and pretty obscure EOF behavior, see commit ac8f3bf8832a # ("n_tty: Fix poll() after buffer-limited eof push read") and commit # 40d5e0905a03 ("n_tty: Fix EOF push handling"). # # And the reason for the EOL confusion is that we treat EOF as a special # EOL condition, with the EOL character being NUL (aka "__DISABLED_CHAR" # in the kernel sources). # # So that EOF look-ahead also affects the normal EOL handling. # # This patch just removes the look-ahead that causes problems, because EOL # is much more critical than the historical "EOF in the middle of a line # that coincides with the end of the buffer" handling ever was. # # Now, it is possible that we should indeed re-introduce the "look at next # character to see if it's a EOF" behavior, but if so, that should be done # not at the kernel buffer chunk boundary in canon_copy_from_read_buf(), # but at a higher level, when we run out of the user buffer. # # In particular, the place to do that would be at the top of # 'n_tty_read()', where we check if it's a continuation of a previously # started read, and there is no more buffer space left, we could decide to # just eat the __DISABLED_CHAR at that point. # # But that would be a separate patch, because I suspect nobody actually # cares, and I'd like to get a report about it before bothering. # # Fixes: 3b830a9c34d5 ("tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer") # Fixes: ac8f3bf8832a ("n_tty: Fix poll() after buffer-limited eof push read") # Fixes: 40d5e0905a03 ("n_tty: Fix EOF push handling") # Link: https://bugzilla.kernel.org/show_bug.cgi?id=215611 # Reported-and-tested-by: Daniel Gibson # Cc: Peter Hurley # Cc: Greg Kroah-Hartman # Cc: Jiri Slaby # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/korg/gcc-11.1.0-nolibc/sparc64-linux/bin/sparc64-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-11.1.0-nolibc/sparc64-linux/bin/sparc64-linux-ld --version # < git log --format=%s --max-count=1 3593030761630e09200072a4bd06468892c27be3 # < make -s -j 32 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.1.0-nolibc/sparc64-linux/bin/sparc64-linux- allmodconfig # Added to kconfig CONFIG_64BIT=n # Added to kconfig CONFIG_BUILD_DOCSRC=n # Added to kconfig CONFIG_HAVE_FTRACE_MCOUNT_RECORD=n # Added to kconfig CONFIG_SAMPLES=n # Added to kconfig CONFIG_MODULE_SIG=n # < make -s -j 32 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.1.0-nolibc/sparc64-linux/bin/sparc64-linux- help # make -s -j 32 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.1.0-nolibc/sparc64-linux/bin/sparc64-linux- olddefconfig # make -s -j 32 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.1.0-nolibc/sparc64-linux/bin/sparc64-linux- :1517:2: warning: #warning syscall clone3 not implemented [-Wcpp] /kisskb/src/arch/sparc/mm/srmmu.c: In function 'smp_flush_page_for_dma': /kisskb/src/arch/sparc/mm/srmmu.c:1639:13: error: cast between incompatible function types from 'void (*)(long unsigned int)' to 'void (*)(long unsigned int, long unsigned int, long unsigned int, long unsigned int, long unsigned int)' [-Werror=cast-function-type] 1639 | xc1((smpfunc_t) local_ops->page_for_dma, page); | ^ /kisskb/src/arch/sparc/mm/srmmu.c: In function 'smp_flush_cache_mm': /kisskb/src/arch/sparc/mm/srmmu.c:1662:29: error: cast between incompatible function types from 'void (*)(struct mm_struct *)' to 'void (*)(long unsigned int, long unsigned int, long unsigned int, long unsigned int, long unsigned int)' [-Werror=cast-function-type] 1662 | xc1((smpfunc_t) local_ops->cache_mm, (unsigned long) mm); | ^ /kisskb/src/arch/sparc/mm/srmmu.c: In function 'smp_flush_tlb_mm': /kisskb/src/arch/sparc/mm/srmmu.c:1674:29: error: cast between incompatible function types from 'void (*)(struct mm_struct *)' to 'void (*)(long unsigned int, long unsigned int, long unsigned int, long unsigned int, long unsigned int)' [-Werror=cast-function-type] 1674 | xc1((smpfunc_t) local_ops->tlb_mm, (unsigned long) mm); | ^ /kisskb/src/arch/sparc/mm/srmmu.c: In function 'smp_flush_cache_range': /kisskb/src/arch/sparc/mm/srmmu.c:1694:29: error: cast between incompatible function types from 'void (*)(struct vm_area_struct *, long unsigned int, long unsigned int)' to 'void (*)(long unsigned int, long unsigned int, long unsigned int, long unsigned int, long unsigned int)' [-Werror=cast-function-type] 1694 | xc3((smpfunc_t) local_ops->cache_range, | ^ /kisskb/src/arch/sparc/mm/srmmu.c: In function 'smp_flush_tlb_range': /kisskb/src/arch/sparc/mm/srmmu.c:1711:29: error: cast between incompatible function types from 'void (*)(struct vm_area_struct *, long unsigned int, long unsigned int)' to 'void (*)(long unsigned int, long unsigned int, long unsigned int, long unsigned int, long unsigned int)' [-Werror=cast-function-type] 1711 | xc3((smpfunc_t) local_ops->tlb_range, | ^ /kisskb/src/arch/sparc/mm/srmmu.c: In function 'smp_flush_cache_page': /kisskb/src/arch/sparc/mm/srmmu.c:1726:29: error: cast between incompatible function types from 'void (*)(struct vm_area_struct *, long unsigned int)' to 'void (*)(long unsigned int, long unsigned int, long unsigned int, long unsigned int, long unsigned int)' [-Werror=cast-function-type] 1726 | xc2((smpfunc_t) local_ops->cache_page, | ^ /kisskb/src/arch/sparc/mm/srmmu.c: In function 'smp_flush_tlb_page': /kisskb/src/arch/sparc/mm/srmmu.c:1741:29: error: cast between incompatible function types from 'void (*)(struct vm_area_struct *, long unsigned int)' to 'void (*)(long unsigned int, long unsigned int, long unsigned int, long unsigned int, long unsigned int)' [-Werror=cast-function-type] 1741 | xc2((smpfunc_t) local_ops->tlb_page, | ^ /kisskb/src/arch/sparc/mm/srmmu.c: In function 'smp_flush_page_to_ram': /kisskb/src/arch/sparc/mm/srmmu.c:1756:13: error: cast between incompatible function types from 'void (*)(long unsigned int)' to 'void (*)(long unsigned int, long unsigned int, long unsigned int, long unsigned int, long unsigned int)' [-Werror=cast-function-type] 1756 | xc1((smpfunc_t) local_ops->page_to_ram, page); | ^ /kisskb/src/arch/sparc/mm/srmmu.c: In function 'smp_flush_sig_insns': /kisskb/src/arch/sparc/mm/srmmu.c:1767:21: error: cast between incompatible function types from 'void (*)(struct mm_struct *, long unsigned int)' to 'void (*)(long unsigned int, long unsigned int, long unsigned int, long unsigned int, long unsigned int)' [-Werror=cast-function-type] 1767 | xc2((smpfunc_t) local_ops->sig_insns, | ^ cc1: all warnings being treated as errors make[3]: *** [/kisskb/src/scripts/Makefile.build:288: arch/sparc/mm/srmmu.o] Error 1 make[3]: *** Waiting for unfinished jobs.... make[2]: *** [/kisskb/src/scripts/Makefile.build:550: arch/sparc/mm] Error 2 make[2]: *** Waiting for unfinished jobs.... make[1]: *** [/kisskb/src/Makefile:1831: arch/sparc] Error 2 make[1]: *** Waiting for unfinished jobs.... /kisskb/src/crypto/blake2b_generic.c: In function 'blake2b_compress_one_generic': /kisskb/src/crypto/blake2b_generic.c:109:1: error: the frame size of 2288 bytes is larger than 2048 bytes [-Werror=frame-larger-than=] 109 | } | ^ cc1: all warnings being treated as errors make[2]: *** [/kisskb/src/scripts/Makefile.build:288: crypto/blake2b_generic.o] Error 1 make[1]: *** [/kisskb/src/Makefile:1831: crypto] Error 2 make: *** [Makefile:219: __sub-make] Error 2 Command 'make -s -j 32 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.1.0-nolibc/sparc64-linux/bin/sparc64-linux- ' returned non-zero exit status 2 # rm -rf /kisskb/build/linus_sparc-allmodconfig_sparc64-gcc11 # Build took: 0:09:28.105536