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Message-ID: <alpine.DEB.2.20.1712210808110.20260@hsp> Date: Wed, 27 Dec 2017 13:39:54 +0100 (CET) From: Lukas Bulwahn <lukas.bulwahn@...il.com> To: Masahiro Yamada <yamada.masahiro@...ionext.com> cc: Nicholas Mc Guire <der.herr@...r.at>, Lukas Bulwahn <lukas.bulwahn@...il.com>, Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>, sil2review@...ts.osadl.org, Michal Marek <michal.lkml@...kovi.net>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Alexey Dobriyan <adobriyan@...il.com> Subject: Re: [SIL2review] [PATCH] fixdep: free memory on second error path of do_config_file On Mon, 18 Dec 2017, Masahiro Yamada wrote: > 2017-12-15 17:23 GMT+09:00 Nicholas Mc Guire <der.herr@...r.at>: >> On Thu, Dec 14, 2017 at 08:54:10PM +0100, Lukas Bulwahn wrote: >>> Commit dee81e988674 ("fixdep: faster CONFIG_ search") introduces the memory >>> leak when `map = mmap(...)` was replaced with `map = malloc(...)` and >>> `read(fd, map, ...)`. It introduces a new second error path, which does not >>> free the allocated memory for `map`. We now correct that behavior and free >>> `map` before the do_config_file() function returns. >>> >>> Facebook's static analysis tool Infer (http://fbinfer.com) found this >>> memory leak: >>> >>> scripts/basic/fixdep.c:297: error: MEMORY_LEAK >>> memory dynamically allocated by call to `malloc()` at line 290, \ >>> column 8 is not reachable after line 297, column 3. >>> >>> Fixes: dee81e988674 ("fixdep: faster CONFIG_ search") >>> >>> Signed-off-by: Lukas Bulwahn <lukas.bulwahn@...il.com> >> Reviewed-by: Nicholas Mc Guire <der.herr@...r.at> >> >>> --- >>> scripts/basic/fixdep.c | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c >>> index bbf62cb..131c450 100644 >>> --- a/scripts/basic/fixdep.c >>> +++ b/scripts/basic/fixdep.c >>> @@ -296,6 +296,7 @@ static void do_config_file(const char *filename) >>> if (read(fd, map, st.st_size) != st.st_size) { >>> perror("fixdep: read"); >>> close(fd); >>> + free(map); >> >> This looks reasonable but actually it is not clear why do_config_file() >> should return at all if read fails as the read error would go unnoticed >> in the current code and allow the build to continue. so this probably >> should be an exit(2) here and not a return which would then take care >> of the free() anyway. > > I agree. > > This should be exit(2). > > You can also remove close() as well since > the operation system will close it anyway. > > > >> Atleast I do not see the rational to allow continuation if the read >> failed as the file should not be empty nor a mismatch with st.st_size >> expected. If it were due to a EINTR then it still should terminate as >> EINTR was not handled and we thus could miss a valid dependency. >> >> Note: this probably also should be applied to the if (!map) condition >> before as well, as at that point it is known that map > 0 and a malloc() >> failure would allow skipping parse_config_file() for a valid config. > > I agree. We should change this too. > I created a new patch with your requested changes, but I did not consider it a second version of this patch by the time of writing. You can find the new patch at: v1: https://patchwork.kernel.org/patch/10126547/ v2: https://patchwork.kernel.org/patch/10128297/ This patch here is now superseded by the new patch. So, this patch here can be abandoned. Lukas
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