Linux 4.1.52

2018-05-28T02:26:45+00:00

Signed-off-by: Sasha Levin

kbuild: disable clang's default use of -fmerge-all-constants

2018-05-23T01:33:54+00:00

[ Upstream commit 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79 ] Prasad reported that he has seen crashes in BPF subsystem with netd on Android with arm64 in the form of (note, the taint is unrelated): [ 4134.721483] Unable to handle kernel paging request at virtual address 800000001 [ 4134.820925] Mem abort info: [ 4134.901283] Exception class = DABT (current EL), IL = 32 bits [ 4135.016736] SET = 0, FnV = 0 [ 4135.119820] EA = 0, S1PTW = 0 [ 4135.201431] Data abort info: [ 4135.301388] ISV = 0, ISS = 0x00000021 [ 4135.359599] CM = 0, WnR = 0 [ 4135.470873] user pgtable: 4k pages, 39-bit VAs, pgd = ffffffe39b946000 [ 4135.499757] [0000000800000001] *pgd=0000000000000000, *pud=0000000000000000 [ 4135.660725] Internal error: Oops: 96000021 [#1] PREEMPT SMP [ 4135.674610] Modules linked in: [ 4135.682883] CPU: 5 PID: 1260 Comm: netd Tainted: G S W 4.14.19+ #1 [ 4135.716188] task: ffffffe39f4aa380 task.stack: ffffff801d4e0000 [ 4135.731599] PC is at bpf_prog_add+0x20/0x68 [ 4135.741746] LR is at bpf_prog_inc+0x20/0x2c [ 4135.751788] pc : [] lr : [] pstate: 60400145 [ 4135.769062] sp : ffffff801d4e3ce0 [...] [ 4136.258315] Process netd (pid: 1260, stack limit = 0xffffff801d4e0000) [ 4136.273746] Call trace: [...] [ 4136.442494] 3ca0: ffffff94ab7ad584 0000000060400145 ffffffe3a01bf8f8 0000000000000006 [ 4136.460936] 3cc0: 0000008000000000 ffffff94ab844204 ffffff801d4e3cf0 ffffff94ab7ad584 [ 4136.479241] [] bpf_prog_add+0x20/0x68 [ 4136.491767] [] bpf_prog_inc+0x20/0x2c [ 4136.504536] [] bpf_obj_get_user+0x204/0x22c [ 4136.518746] [] SyS_bpf+0x5a8/0x1a88 Android's netd was basically pinning the uid cookie BPF map in BPF fs (/sys/fs/bpf/traffic_cookie_uid_map) and later on retrieving it again resulting in above panic. Issue is that the map was wrongly identified as a prog! Above kernel was compiled with clang 4.0, and it turns out that clang decided to merge the bpf_prog_iops and bpf_map_iops into a single memory location, such that the two i_ops could then not be distinguished anymore. Reason for this miscompilation is that clang has the more aggressive -fmerge-all-constants enabled by default. In fact, clang source code has a comment about it in lib/AST/ExprConstant.cpp on why it is okay to do so: Pointers with different bases cannot represent the same object. (Note that clang defaults to -fmerge-all-constants, which can lead to inconsistent results for comparisons involving the address of a constant; this generally doesn't matter in practice.) The issue never appeared with gcc however, since gcc does not enable -fmerge-all-constants by default and even *explicitly* states in it's option description that using this flag results in non-conforming behavior, quote from man gcc: Languages like C or C++ require each variable, including multiple instances of the same variable in recursive calls, to have distinct locations, so using this option results in non-conforming behavior. There are also various clang bug reports open on that matter [1], where clang developers acknowledge the non-conforming behavior, and refer to disabling it with -fno-merge-all-constants. But even if this gets fixed in clang today, there are already users out there that triggered this. Thus, fix this issue by explicitly adding -fno-merge-all-constants to the kernel's Makefile to generically disable this optimization, since potentially other places in the kernel could subtly break as well. Note, there is also a flag called -fmerge-constants (not supported by clang), which is more conservative and only applies to strings and it's enabled in gcc's -O/-O2/-O3/-Os optimization levels. In gcc's code, the two flags -fmerge-{all-,}constants share the same variable internally, so when disabling it via -fno-merge-all-constants, then we really don't merge any const data (e.g. strings), and text size increases with gcc (14,927,214 -> 14,942,646 for vmlinux.o). $ gcc -fverbose-asm -O2 foo.c -S -o foo.S -> foo.S lists -fmerge-constants under options enabled $ gcc -fverbose-asm -O2 -fno-merge-all-constants foo.c -S -o foo.S -> foo.S doesn't list -fmerge-constants under options enabled $ gcc -fverbose-asm -O2 -fno-merge-all-constants -fmerge-constants foo.c -S -o foo.S -> foo.S lists -fmerge-constants under options enabled Thus, as a workaround we need to set both -fno-merge-all-constants *and* -fmerge-constants in the Makefile in order for text size to stay as is. [1] https://bugs.llvm.org/show_bug.cgi?id=18538 Reported-by: Prasad Sodagudi Signed-off-by: Daniel Borkmann Cc: Linus Torvalds Cc: Chenbo Feng Cc: Richard Smith Cc: Chandler Carruth Cc: linux-kernel@vger.kernel.org Tested-by: Prasad Sodagudi Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin

Linux 4.1.51

2018-03-27T20:15:21+00:00

Signed-off-by: Sasha Levin

Linux 4.1.50

2018-03-05T21:35:54+00:00

Signed-off-by: Sasha Levin

kbuild: add '-fno-stack-check' to kernel build options

2018-03-01T00:32:18+00:00

[ Upstream commit 3ce120b16cc548472f80cf8644f90eda958cf1b6 ] It appears that hardened gentoo enables "-fstack-check" by default for gcc. That doesn't work _at_all_ for the kernel, because the kernel stack doesn't act like a user stack at all: it's much smaller, and it doesn't auto-expand on use. So the extra "probe one page below the stack" code generated by -fstack-check just breaks the kernel in horrible ways, causing infinite double faults etc. [ I have to say, that the particular code gcc generates looks very stupid even for user space where it works, but that's a separate issue. ] Reported-and-tested-by: Alexander Tsoy Reported-and-tested-by: Toralf Förster Cc: stable@kernel.org Cc: Dave Hansen Cc: Jiri Kosina Cc: Andy Lutomirski Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

Linux 4.1.49

2018-01-22T20:40:06+00:00

Signed-off-by: Sasha Levin

disable new gcc-7.1.1 warnings for now

2018-01-17T17:55:41+00:00

[ Upstream commit bd664f6b3e376a8ef4990f87d08271cc2d01ba9a ] I made the mistake of upgrading my desktop to the new Fedora 26 that comes with gcc-7.1.1. There's nothing wrong per se that I've noticed, but I now have 1500 lines of warnings, mostly from the new format-truncation warning triggering all over the tree. We use 'snprintf()' and friends in a lot of places, and often know that the numbers are fairly small (ie a controller index or similar), but gcc doesn't know that, and sees an 'int', and thinks that it could be some huge number. And then complains when our buffers are not able to fit the name for the ten millionth controller. These warnings aren't necessarily bad per se, and we probably want to look through them subsystem by subsystem, but at least during the merge window they just mean that I can't even see if somebody is introducing any *real* problems when I pull. So warnings disabled for now. Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

Linux 4.1.48

2017-12-12T15:21:44+00:00

Signed-off-by: Sasha Levin

Linux 4.1.47

2017-12-07T02:20:16+00:00

Signed-off-by: Sasha Levin

Linux 4.1.46

2017-11-08T03:44:28+00:00

Signed-off-by: Sasha Levin

kernel/git/stable/linux.git/Makefile, branch linux-4.1.y

Linux 4.1.52

kbuild: disable clang's default use of -fmerge-all-constants

Linux 4.1.51

Linux 4.1.50

kbuild: add '-fno-stack-check' to kernel build options

Linux 4.1.49

disable new gcc-7.1.1 warnings for now

Linux 4.1.48

Linux 4.1.47

Linux 4.1.46